The u-brake is b-a-c-k (and it's mad!)

[PurpleFrog]

The only reason we don't see discs in the tours is because they're currently outlawed by the UCI due to safety concerns. What these concerns are I have no idea.

A cynic would say that the UCI want there to be as many types of bicycle subspecies as possible to increase sales. A disc frame that mamils could tour on and use for cross, winter training and road racing without embarrassment could be several sales lost.