Modelmaking, especially R/C based went through a period of huge expansion in the '70's and '80's, with the advent of affordable and reliable proportional radio equipment, and began to diminish soon after. Every dog has its day, as they say.
Computers, with their inherent 'instant-sunshine' entertainment benefit and the lever of big business has undoubtedly had an impact on other pursuits. However, I believe society in general has become increasingly consumerist over the past three decades, and this has been encouraged by governments and the media, no doubt believing they can keep economies buoyant surfing an ocean of debt!
Hobbies like modelmaking are often portrayed negatively in popular culture, which does nothing to enhance its appeal to younger people.
Having said all that, the range and quality of products available now has never been better. Someone must be buying all this stuff, otherwise it would never see the light of day. A lot of these products appear to be of the RTR ilk, which fits in well with the modern ethic of 'buy it, use it, break it, bin it, buy new' prevalent in the world of today.
My thoughts are that the balance of power in this hobby has shifted away from traditional shows, magazines, clubs and societies, and moved towards the internet.
Twenty years ago, if you wanted to look at a wide range of products, a show was the only practical way to do it- now you can click on websites with a mouse, look at videos, pictures of the kit in action, order it and have it delivered to your door, from anywhere in the World.
In addition, shows used to be great places to pick-up a bargain or two. This is no longer the case, with most businesses charging their normal rates.
In regards clubs and societies, prior to the internet, if you wanted information on a pursuit such as this, especially something niche like submarines there were three ways of going about it- specialist commercial publication, visit a show, or join a club or society. Now we have free forums (like this one) social networking sites, Youtube/Vimeo, email etc. These offer the user far more interaction than older methods, and you also getter a broader opinion.