As a bike-mechanic, I feel I should, and do, stop to assist someone with a mechanic problem - including patching wheels. I carry a Topeak Alien II multi-tool and assorted other tools. Of course where I live, the people are friendly and cordial. And we have no gun laws - so people are VERY polite.
I also took an EMT course - should I encounter a person who has fallen apart. One day I got to ply both skills. A kid (late teens) crashed on his new Cannondale in front of my place, and hit his head in the bargain - no helmet. He didn't want to bother me, but I read him the head-trauma what-to-look-for list. And I torqued the bolts that came loose on the Cannondale.