Another data point: I play the organ, which involves playing a large keyboard with your feet (https://en.m.wikipedia.org/wiki/Pedal_keyboard). The structure of black notes is crucial to being able to play without looking (which is important because you’re simultaneously doing various other things). Concretely, I couldn’t imagine playing the organ without being able to slam my foot into the right hand side of a B flat in order to know that my foot is on top of the B. If you watch an experienced organist’s feet you’ll see them do this all the time.
Another data point: I play the organ, which involves playing a large keyboard with your feet (https://en.m.wikipedia.org/wiki/Pedal_keyboard). The structure of black notes is crucial to being able to play without looking (which is important because you’re simultaneously doing various other things). Concretely, I couldn’t imagine playing the organ without being able to slam my foot into the right hand side of a B flat in order to know that my foot is on top of the B. If you watch an experienced organist’s feet you’ll see them do this all the time.
I also find C major horrible.