I don't think it counts as "nobody watching" since many people saw it technically, but I will often pull over to ask if people on the side of the highway need help as long as I'm not running late for something.
I helped a Hispanic guy recently change his tire since he apparently misplaced his lug nut wrench and he had a blowout. I let him use mine and I topped off the air in his spare that was a little low. Took me a little while to figure out what he needed since he didn't speak a word of English and I failed Spanish 3 times, but we got there using Google translate, hand signals and grunts haha.
I do it because I hope that if one day I was stranded on the side of the road (and somehow without all the tools I always carry around) that someone would be nice enough to stop and offer assistance.
Be the change you want to see in the world n all that.