Man, that's awful. I always stop, or at least exchange thumbs up, and I've had people stop for me before. Bici or moto. Unless someone's on the phone and obviously uninjured, then I'll figure they have things under control.

Even on an organized ride, I stopped, offered a tandem couple my chain tool (they declined, they had apparently had who knows how many mechanicals already and were just fed up and ready to take the sag) - and then I rode on to the next support vehicle and made sure that they knew the couple was back there.

Most embarrassing time I was the recipient of the offer of help was when I got a flat on the bike path. I couldn't get my CO2 inflater to work (turns out it wasn't me, it was a wonky head that I eventually threw out), so I was using my mini pump, which takes forever under the best of circumstances; and the first time I hadn't got the tire bead seated properly, so I had to deflate it and do it all over again. I had just started pumping the first time when a guy on a TT bike threw an offer of help over his shoulder. Twenty minutes later, after he'd been to the end of the bike path and back, he came back the other direction and again asked if I needed anything. "Same flat?" he asked incredulously (and I'm sure he thought I really did need help and was just too proud to accept).