Originally Posted by
dmanthree
And wheels need to be more robust since braking stress is now transferred to the spokes and rims. This is why you rarely see a disc brake bike with fewer than 24 spokes on either wheel.
It's more because of the dishing. Disc wheels need to be dished so much it makes them weaker. Especially the front, since a wheel for a rim brake doesn't even need to be dished.