I guess I don't get why people wouldnt go out with out a spare tube, small patch kit, and air of some kind plus a tire lever. The things might be "bulky" but will save you those times that you need it.

I was out with a guy just this morning who had a flat, changed it, aired it up with 1 of the two co2 cartridges he had and he did it in a rush. Ten miles down the road, he had another flat, dealt with it and then tried to air it up with his second co2 cartridge just to find out it was a dud.