Every artist is now the star of his or her own movie.
To have art colonies, you have to have artists as outcasts, which, of course, really didn't happen until Romanticism. But now, because of the lifestyle revolution, artists aren't outcasts anymore. Mothers and fathers used to weep when their offspring announced they wanted to be artists. Now the folks just send their kids to Yale and put a down-payment on a loft.
But why would artists want to hang around with one another? The past is a weird place. Artists used to cluster. Certainly, a common belief-system would explain a lot, along with mutual protection, sharing information, hopping on to one or another stylistic train, mate-swapping, binge-ing, philandering and the thrill of hand-to-hand competition. Artists learn from each other. And, according to Romanticism, they need inspiration: a muse, a myth, a drug, or a landscape.
There are no more art colonies because we no longer need them. We fly here; we fly there. We form our own little art networks. There are no art colonies for the same reason there are no art bars. Where is the Cedar Bar or the Max's of yesteryear?
Young artists used to pray for Pollock, de Kooning, or Barney Newman sightings. Nowadays, I don't think anyone would blink an eye at spying Jeff Koons or Matthew Barney. Every artist is now the star of his or her own movie.
No one wants to talk. If you go out, you go to a club to dance your brains out. Art now is serious business; you cannot risk being seen drunk in public, being heard saying something passionate -- or saying something really, really stupid. Groupies might be carrying guns. Your image is all.