The car hobby is dying? I'd argue that it's bigger now than ever.
While the traditional fairground car show "sit in the lawn chair and polish the chrome" car guys may be dwindling off a bit, car culture is surviving in many other ways. Cars are all over social media, traditional media, and more. There are more racing events and car meets/shows for the Average Joe to attend and participate in now than there were 20-30 years ago. There are car clubs and organizations all over the place that didn't exist 10 years ago, mainly thanks to the internet. Facebook, while viewed as The Great Satan by some people, is great for this. I'm in a number of large groups on there, and some have a cult-like following and grow larger by the week.
When someone does something "cool", it's 10 seconds away from being broadcast over the world, and copycats can view a forum post or videos that will help them do the same thing. Whenever a trend appears, for better or worse, everyone knows in a couple days' time. It's incredible.
While print media has been on the decline, magazines like GRM (of course!), Hot Rod, and Hemmings are still going strong, and each has an online component that spreads the word further and faster. I write for a blog now, and I've seen our reader base grow through social media "likes" and web traffic, even since I started earlier this year. I'm seeing a lot of younger guys get into it too. It's definitely not just an old folks hobby.
Now, since I'm a car guy, I have a general awareness of what's going on in the car culture, but the general public doesn't. Why? Because that's the way society is today; it's the message that the popular media conveys. General apathy for many things is just the way of the world now; people can't be bothered. Look at the music world, for example. There's a lot of people that think music is dead. That's because they are not looking in the right places. Yes, the internet did have a great effect on the rock stars and pop stars of old, and some argue that the album format is on the way out. If you look under the surface, it's still there and thriving.
The issue here is that the internet and social media has basically compartmentalized what people like and don't like, and made it easy to forget that things that everyone used to be aware of still exist. If the sheep don't "like" something on your social media feed, they may not see it. That doesn't mean it's dying or dead!