and certain niches are getting smaller, people move on, die, or tire of it... others prefer what they grew up with.
Well yeah that's the whole point of this thread. Young people don't care about older cars because older people have failed to make them important.
That's basically true, but I've noticed that, psychologically, people are only really attracted to the idea of getting a nice car if they can own it. Thus I do not think the fact that they are not renting these cars proves a disinterest in cars relative to the older generation. If you don't believe this, find a man that is interested in owning sports cars and ask him why he doesn't just rent them, "Wouldn't that make more practical sense?" You'll just get a blank stare from him and he won't know what to say. (And no, he's not going to change his patterns or take the advice either)