The social networks are fickle and self-consciously sarcastic (see the recent potato salad phenomenon). They are not about arrow-through-the-heart sincerity. That's why YouTube made Psy a star, but it couldn't have been the medium for Beatlemania. Justin Timberlake has 32.9 million Twitter followers, but he's no Jack White.
In the music industry's heyday, it produced a lot of schlock. But it got great music out to the masses, too. These days, it expects artists to do their own promotion and for those who less good at that than at making music, it may mean not getting heard. For fans it means less good music to stream and download. Well, there's always the warm and fuzzy world of vinyl nostalgia, I guess.