I think there's a difference between not wanting to be on social media...and not wanting to be on some loser's cheesy "family-friendly" Youtube channel alongside his grandparents and his disabled little sister.
That said, I do still watch a lot of the college-age or recently graduated vloggers that I found back when I was looking for study inspo for nursing school...and very few of them feature their friends on their vlogs in any meaningful way. I don't think 20somethings want their private business out there on the internet any more than the rest of us do.