Those that ask before sitting down on a bench next to you and those who just plonk themselves down.
I don't know if I'm more tetchy about it because I'd COVID. We are outside obviously, in a public area So risk isn't high.
I wouldn't dream at sitting down on someone's picnic bench without saying hello/asking did they mind.
It's just good manners isn't it? I'm from London so don't enjoy talking to strangers
but I would still ask!