In their possible defense...It seems that you were walking with your bike when they passed. They may have not noticed you had a blown tired. I'm not likely to speak to someone walking with their bike (unless she's cute). However, if their bike is laid down or it looks like they're working on it, I'm more inclined to offer assistance.
As for carrying a spare tire, I do not. I snake bit a tire last year, at the furthest point from home on a 75 mile ride, no less. Anyway, I only changed the tube and it survived the ride home. There is also the dollar bill trick that I've been educated on since then. A tube wrapped with a dollar bill will keep a tube from pushing out of a blown out tire. I now carry a bill in my bag at all times.