The horn thing doesn't seem like that big a deal actually. I've never used the horn in a potential accident situation because there's always something better I could be focusing on to avoid the accident. As pilot say: aviate, navigate, then communicate. [0] Some studies seems to support that [1].
The only accidents I can imagine the horn preventing are ones where you are stationary, which almost always means the other car is moving slowly - like somebody backing into you in a parking lot. Overall pretty low consequence incidents.
So to the extent that horn use is nearly all elective rather than emergency, is antisocial and has few benefits: make it a small, hard-to-reach button.
(With important exceptions like heavy vehicles that can't maneuver well and non-Western driving cultures that rely on routine horn use to communicate intentions.)
[0] Granted aircraft have an extra dimension to play in for collision-avoidance.
[1] https://slate.com/technology/2008/11/honk-if-you-know-why-yo...