A lot of people think it's too cold to climb in Yosemite in the winter. I don't know why. The Valley floor is the same altitude as Bishop, Jtree and Red Rocks, but I guess it's probably for the best. The Eastside towns could use the money, and the Valley could use a break.
Or maybe people are just tired of the circuits at their "weekend" crag and want to travel somewhere for winter break.