The customer base (AKA 'the market') has changed. Successful businesses follow the dough. When the dough begins to dry up here, you scout around and find out where more of it is flowing. The younger blood meant for the hobby, the really new folks (and not those somewhat seasoned by Dad's old layout and ideas) are used to shopping for stuff on shelves that requires scissors to cut into blister pack, insert batteries, and play away. Trains now have to compete against virtual reality-like games with intense graphics and sounds.
The manufacturers have come and gone in some cases, and in the comers have also arrived some new ideas. Broadway Limited got sound into steam in the first big way. People began to do serious imagery of refined modelling based on improved ideas spread by the internet. With a desire to improve imagery, especially the realism, the models themselves had to improve in appearance. RP-25 wheels became the standard, and Proto 87 is probably going to supplant a lot of that older standard in the next few years when more people show off models in imagery with highly realistic details...such as tire profiles, flanges, and turnouts.
Also, people who earn $75-200K a year are plentiful. After they get a motor home, a pool, and a snowmobile, they look for some other diversion. It may be RC, trains, fancy internet gaming....but they want easy diversion, and they like to be able to wow their friends with the 'best and fanciest'.
DCC has come into its own in just the past maybe four or five years. Forums such as this are often replete with questions from people, not just newbies, who want a DCC question answered. Somehow, to those more than a few months in the hobby, pizza cutter flanges and poor molded details on boilers just don't seem to jive with 'digital'.
In a nutshell, it is a confluence of forces that began when the first RTR Christmas card and tree decorations came on the market...no more stinging popcorn.
(To that last, some of you are more like

. Understood. It that was what made Christmas, or your hobby, change away from that is going to be hard on you.)
-Crandell