FWIW (likely not much!), my last car was a Mercedes Benz, and it was also difficult to honk that car's horn. The fact that Tesla buys its steering wheel and steering column assembly from Daimler Benz is probably why the horn is difficult to use -- maybe it is a Benz thing. Or more likely, it is a result of all the "stuff" on the steering wheel (audio controls and sop on, plus the airbag) and how little real estate was left for horn switches....