IMHO, this is a microcosm of a couple of other threads here on the forum...
1) Walmart effect = long before there was the Internet and online retailers there was mailorder houses, which fine for the guys that didn't have a LHS but oftentimes guys that could order parts somewhere else helped (Tower, Horizon, etc.) grow into the megasuppliers they are today that can afford to dominate the hobby. So in the same manner that mom-&-pop hardware stores got squeezed out of the local retail market, the same thing has happend with the vast majority of local hobby shops.
2) Mark-up = long ago it used to be that the price (MSRP) that you saw on the box was the price of the carkit, or at least close - but nowadays there is no money to be made in carkits, versus the cost of them relative to overall inventory. For all intents and purposes the only reason shops stock any kits is just to bring people in the store, but they can't afford to carry the number they once did. Parts are where its at now, since they do for for full retail, while shops only make 10% or less on kits.
3) old vs. new = in much the same manner that real car junkyards and autoparts businesses carry the majority of their inventory based on current (10 years old or newer) vehicles, there is little reason for these businesses to carry what is called "dead inventory" (i.e. stuff that doesn't sell in volume, since most vehicles on the road today are relatively new). There is no money, except on fleaBay, in old parts they don't know when they might sell them.
4) Slot cars = back in the day slotcars were all the rage, and slotcar tracks littered almost every town and city (big and small) in the country. There was a big boom in the 1960s, that died out, that then boomed again in the 1980s - and hobby shops put in slotcar tracks in droves. It was cheap, and there existed a natural progression from slotcars to RC cars -- because the guys racing their slot cars saw the bigger and more realistic RC cars that weren't controlled by a wire or on a slot in a little track. Some of the biggest slotcar tracks that survived from the '60s into the '80s that housed 4 or 5 tracks under one roof (INDY Slots in Indianapolis Indiana for example) now house one smallish indoor RC track, and another dirt one outdoors, but as slotcars grew away from favor of the general public and RC racing superceeded them....... and now places simply can't afford RC tracks because of the afformentioned insurance issue.
5) Traxass effect 1 = while great in premise for themselves, the RTR market is all but responsible for killing the aftermarket parts market. Long ago there were literally hundreds of aftermarket parts companies in business, it's how Losi got into the biz, making doo-dads and what-nots for half the cars on the market. But since most kits today come preassembled, and there is no need for anything else to get it running, there is no motivation for people to add anything to their cars/trucks.
6) Traxass effect 2 = it used to be that there was a difference between the toy grade RCs and the hobby grade RCs, the toys were sold at RadioShack and were for bashers and the hobbygrades were sold at hobby shops for racers. But again, since most buyers today can buy a RTR car/truck out of the box and take it straight home and run it as is it leaves little motivation fo people to buy anything else for it. Most of these buyers today are one-and-done. And since it's long been said that racers only make up 10% or less of the actual market there is little reason for anyone to spend the marketing or manufacturing to make a race-specific kit.
7) Bashers = while many people THINK the basher segment of this hobby helps attract people to the hobby they never have and they never will. Back in the day regularly we'd see some father and son wander into a hobby shop or stop at a local track to run after purchasing a toy grade RC car, only to be dismayed in one manner or another at the price to actually go racing - and these guys never came back just like they don't come back today. For the most part once they've broken their traxass or whatever it gets socked away in the closet like every other toy the kid's broken over the years.
kids = today's young people grew up with video games, so in the same manner that the bicycle market is in the crapper (when was the last time you saw a gang of kids cruising the neighborhood on their schwinns, or a big pack of them playing football in the nearby vacant lot.......for FUN?) they'd rather race or play football or freaking air guitar on the TV. Kids today don't grow up "playing" and they darn sure don't grow up "working", and the RC hobby used to be work. No more. Kids (and adults) today want instant gratification, and the hobbygrade kits of a bygone era don't fulfill the mentality needed for the hobby to survive longterm.
9) Lack of racing venues = Like it or not, but this "hobby" grew out of racing, but with the move away from racing and into RTRs this has happened for three reasons: a] insurance, it used to be that facilities popped up all over and only required similar blanket insurance coverage that a playground at McDonalds required, but with today's lawsuit-happy society nimrods stood in the middle of the track and got hit and feined injurty (or not) but sued the local shop that funded the track. So now individual businesses can't have a backyard track, their insurance agent refuses to cover it, and any track today built on public or private land has to find its own high-priced coverage (it's ungodly expensive, I've looked) or affiliate itself with ROAR and have all the members/racers be ROAR members to be included under their coverage; b] bashers don't race, and don't support racing. Back in the day many shops had backyard/backshop tracks, and these attracted racers after they got to see how much fun it was to race, but those days are long behind us; c] property costs, with the maniacle rise of the property and housing market over the last 20 years (that's now falling in around us and hurting the economy more than anything individual other thing) has made it all but impractical to put in a track, it's just a bad investment.
10) We've done it to ourselves = 20 years ago it cost about $150 for an RC kit that came with nothing, and actually needed quite a lot to get up and running, whereas nowadays while that cost should be roughly double that (inflation, economic growth) instead that same baisc kit costs (for example) $200 and it comes with a cheap radio, a cheap servo, a cheap ESC -- and (perhaps the biggest abortion of all of it) the damn thing comes preassembled. And YET people still whine about the cost. So IMHO until these RTR kits get back in line with what things should cost we will continue to see a dropoff in manufacturers being involved on a large scale. It's why the owners of both Losi and Associated got out while the getting was good, they saw the handwriting on the walls.
I'm sorry, but people that somehow think the slasher/bash/class is good for the overall growth of this hobby are sadly mistaken. Sure a small percentage of these people will progress into other classes, but the overwhelming vast majority have bought a truck that there is no intrinsic need to fix or replace anything on and they will keep running them like that until the thing dies. And when it does die they won't be back. The hobby as itself took a hit as more and more RTRs hit the market, and none of them were any less raceable than the slash, so by the same token all the slash wil be is the latest fad and fads don't survive the test of time - never have and never will.