> Your experience is unique and frankly strange.
It not happening to you in no way makes it unique or strange. I'm in my mid 30s and have likewise been all around the country and have traveled internationally plenty.
I see everything from well-behaved dogs sitting there doing nothing, to annoying dogs wandering around, stretching to the end of their too-long leash, rubbing against people's legs and going under tables, to actually jumping at (not necessarily on) people's laps. Don't get me wrong, the majority of dogs I see in public places are reasonably well-behaved. But there are enough that aren't where IMO it becomes a big problem.
Perhaps SF's dog owners just suck more than in most other places. I would definitely believe that. Most of the dog owners I know have given their dogs minimal to no useful training and have little control over them aside from what they get just by having them on a leash. Everyone here is "busy" all the time and I wouldn't be surprised that on average they walk their dogs less than people in other places. Add that to small apartment sizes, and you end up with restless dogs that are unable to expend the energy they need to.
And maybe that's it -- I can't remember an instance where this has happened to me outside the bay area. I assumed that was because, since I live here, I have orders of magnitude more experience with restaurants here, but maybe there's more to it than just that.