Road racers with skinny high-pressure tires have limited braking potential on wet roads. Weight is an issue I guess but OTOH I read that superbike manufacturers are limited by UCI weight limit, though I suppose there are other areas where they'd rather put the weight than brakes. Always loved Campy Record brakes which I used to have on my race bikes & even some tourers. So solid with nice modulation & didn't require excessive effort despite pads being same size as competing brands. Once had Universal side-pulls which appeared to be very similar but required huge braking effort. Once read a story in Bike World or Bicycling magazine about Euro-pro racers who would descend down mountains & put their hands on other racers' backs to help slow down--they'd say "Mavic"...supposedly racers forced to use the Mavic gruppo didn't find the brakes too good.

Mud as in cross racing is super slippery but OTOH they don't have additional weight of touring bike + luggage. Even tourists riding in rain get dirt on rims though I suppose it's usually more road grit than fine mud particles.