While pros ride what they are sponsored to ride, the impetus to stop making frames rim brake compatible comes from consumers overwhelmingly buying disc brake bikes.
The vocal minority which bemoans the change just does not buy that many new carbon fiber bikes. Rim brakes aren't going away, there will always be retro stuff enthusiasts and a cottage industry to cater for them, just like you can still get quill stems and square taper cranks and some swear by them.