Huh. I'm going to have to do some polling in my circle but AFAIK honking for I'm Here or Goodbye is quite normal and not considered rude at all. Laying on the horn for several second OTOH, is quite rude.
This is really normal in my family and among my neighbours as well. It's a very short, very quiet honk that has never bothered me when I've heard it (and I'm someone who hates unnecessary noise), and I haven't heard anyone else complain.
How do you have a "very quiet" honk?
My car horn makes the same volume of noise no matter how hard or soft I push on it.
And just because people aren't complaining doesn't mean they don't mind.
I don't think it's polite--it's the equivalent of shouting from the street.
And to say goodbye? Didn't you just say goodbye at the door? How long is the goodbye-ing going to go on?
In the case of the long hard-to-back-out-of driveway, I would think it would be more sensible to simply assume you could get out safely, and that if you *didn't*, you'd honk. I.e., "honk is for danger or trouble," not "honk is for secret codes."