From a practical standpoint, quick release wheels are easier to lock up. I've used a QR skewer on my front wheel for a while, and when i need to lock it up, I take the five seconds to remove it, put it with the rear, and boom - both wheels locked with a u-lock.

It just makes more sense.

There are... strains of obsession with track standards among the fixed gear folk, despite the fact that it's unnecessary. There are also talk of fixed gear riding being "harder on parts," and thus comments about how QRs wouldn't hold up to pedaling forces. Though lz5004 makes a decent point about tensioning a chain tightening the left and right nuts independently of each other.