Hi Mark;
I wouldn't say it's not popular. It's just that the ones who buy have changed. Plus when's the last time you got a model car or plane for less than $ 20.00 bucks?
The kids that have that kind of money spend it on Games or other stuff. I used to do a class at the North Little Rock Community Center. Older adults, even then, liked building Model Cars.
The class expenses were pretty much under thirty bucks. A new Monogram Car kit ( Or plane) and Knife, Glue and a Basic paint set.( I taught them paint color mixing). The same stuff today would be over forty bucks. That's hurt the hobby. The point is The Hobby is one of the few so heavily dependent on the price of a Barrel ( 42 U.S.gallons) of oil.
Plastic is a petroleum based product and the price has gone up over the years. This drives the costs up. Folks that would buy model kits on a weekly basis now have to make it last longer in the build to get( as they see it ) their entertainment Dollar value back out of it.
Then there is another factor and you have heard about it from other replies. ( This is correct or terribly off) I didn't know when I started the hobby back in the wood and plastic day that we would have ( Rivet Counters ) so deeply entrenched in the hobby. I used to love showing off my work.
If I got Honorable mention that was nice. Nowadays, you put a model on the table built OOB you will be terribly disappointed as the interest seems to be centered on the But! look at all the aftermarket stuff, he or she put on it!
This means the average, slightly out of scale, to many panel lines or not enough rivets is gonna disappoint many. Personally, one of the most fun models I have built over the years is the Monogram P-51 and I don't really like planes that much! The next is I think Hasegawa's or Tamiya's ME-262 Clear edition. The clear Plane took me over six months to build. Why? all the detail I added that could be seen and the P-51 because it was just a pleasure to build.
By the way all the detail in the ME-262 came from my scrap box. Nothing aftermarket. I had an Air Force friend show me the differences in Ejection seats and most of my planes benefit from that knowledge. Aftermarket, Why?
Ships , well I don't know about to many ways to re-create 1/350 rails and ladders without going to P.E. There is a method from way back, no one uses now. The ships in the Travel Agency window had rails done with strips of clear plastic with the railing printed on them
I divised a way to do this in scale with artists pens ( Ink) and a T-Square. Worked great til my first I.P.M.S.Show and boy, did I get shot down hard. So there's that. I developed a way to clean up the Inca Pyramid type stairs and add rails to them That worked. For Ladders and hatches I shaved the items off railroad kits close in size and that worked, til Tom's Modelworks, Eduard and Gold Medal models came on the market.
Has modeling slumped? Most definitely! as a regular purchase for the regular family on a tight budget. Son to Dad-" But dad it was $24.00dollars, I couldn't get it" Dad - We'll see. Dad goes to store and sees the model in question. " Well,It didn't cost that much when I bought one in High School "
Times and costs change. It drives the whole market and we have really become, like LEGO, a Niche market! I don't believe it will die out though. I have friends now cranking them out on their 3-D printers!