Originally Posted by Johnk3

This raises several issues.
1) Carbon rims need disc brakes to be safe and avoid undue wear.
2) Disc brakes are heavier, require stronger stays and forks because they are not centered, the braking force tends to torque the frame, and it is annoying to change wheels.
3) If you have a hydraulic leak you are toast.
4) Direct mount rim brakes on alloy rims is a newer solution. They are much stronger and effective than the old style brakes. The weight difference between carbon wheels and alloy wheels and the weight of the disk brakes and the heavier stays and forks end up making the carbon wheels of questionable value unless you are a racer.
5) Direct mount rim brakes have an inherent mechanical advantage over disc brakes. The force it takes to stop a rotating force at 3 or 4 inches is many times that of a rim brake at 12 inches from center.
6) Disc brakes are clodish and ugly. There is nothing remotely elegant about them. The frame connections are ugly.
7) Disk brakes and carbon wheels push the cost of a bike up dramatically.

One major problem with direct mount rim brakes is that you can not just put them on any bike. The frame has to have the connections built in to the fork and stays. See the photos below.