bikingshearer 

Exactly this. I have done this at least a dozen times over the years. I have done other random roadside repairs as well, including truing up a minimally-spoked wheel that had popped a spoke and the spoke tension was so high that the rim deformed so much that it was unrideable; it was good enough to get her home.. Most recently was at Cino 2023, where I gave a tube to another rider and installed with the usual admonition to pay it forward some day and with a gentle suggestion that it is a good idea to know how to fix a flat.

One time during an event ride, I helped a young lady change a tube. She and her friends knew the basics, but could not figure out how to get the tire back on the rim. They handed me some tire levers (like I said, they knew the basics), but I said I'd try putting it on bare-handed first to avoid causing another puncture. The young lady expressed surprise that I might be able to do so. Her male friend said: "Are you kidding? Look at the size of him." (I am not a small person.) Made my day. Well, that and actually succeeding in installing the tire with no levers.

I (almost) always ask someone who looks like they might be having a mechanical if they have everything they need. If they say no, I stop to see if I can help. Usually I can, sometimes I can't. On several occasions, I have come across a rider who had just crashed and did what I could; this generally consists of telling them to stay down until injuries/damage can be assessed, convincing them that continuing their ride is a bad idea, and then helping them call for a ride. On the flip side, twice when I had bad crashes, a motorist going the other way turned around, stopped, made sure I was alright, packed up my bike and me, and drove me 10 or 15 miles out of their way to a safe place (home one time, a motel the other time). More folks are good people than are jerks, although the jerks tend to have an impact on one's day far out of proportion to their numbers.