There's someone who does this every day outside my apartment at around 7:15. It is infuriating. 4-5 loud, inconsistently-spaced honks "just to be sure" when I'm sure their car locks silently on the first request. Most modern cars only beep if you lock them twice.
A neighbor used to come home from work late at night and lock their doors three or four times, and every time it would wake me up. I wish there was a silent door lock and it would just flash the headlights.
Most cars have this if you look in the user manual. Even old cars with no graphical radio have konami-code-like sequences of button presses you can input to turn them off.
Maybe no surprise to learn that, for a person who thinks it acceptable for the horn to sound for no real reason, this would be considered far too much effort?
I turn off the audible alert on lock. Flashing the lights is plenty, why be obnoxious and add noise to the soundscape? I can hear the locks click, anyway.