I think it's also the fact that a lot of the younger VAs actually consume the media they're working on - they watch a ton of anime and play a bunch of games, so they're naturally more excited to talk about their involvement. Older VAs came up in a different time and atmosphere, so they're less likely to know or care as much about that stuff.
Excellent point, I've noticed this too.
NISA has had a habit in recent years of hiring former/current Newgrounds/Lemmingsoft/VA Alliance members too. Some people might complain about 'lack of experience' or whatever, but I think it's great they're getting noticed.
Kira Buckland was basically "that girl who was in Metal Gear Awesome" until you got her for Mugen Souls. Then her career has snowballed ever since. Just as an example.