you've forgotten the northern/southern thing.
There's something in this.
I'm more inclined to wave when riding on my own patch, partly because if I wave at half the cyclists I see on a ride, I might only have to wave twice.
I attempted the same policy on a ride through Oxford, but soon got fed up with it because I was waving every few seconds.
Same with pedestrians on a shared path, in the north there are very few so I will tend to use my voice to alert them when approaching from behind.
Too many to do that down south.
Allied to that is the fact that northerners are more likely to speak to strangers.
I see that all the time, in shops, on public transport, in cafes, and on the bike.
Not sure if it makes northerners more friendly, just keener to acknowledge the existence of others.