vinyl and rubber are two different things. have you ever patched a tube before? it sounds like you haven't. how often do your tubes get "torn at the seams"?
Yes, plenty, a long time ago. Maybe my kit just sucked, but I wasn't impressed. I don't get flats very often(knock on kevlar!) But last week one tube exploded at the seam shortly after being inflated. I thought it was seated well, but who knows.
The bottom line is, on a ride, I am just not in the mood for arts and crafts and I don't feel like carrying both a set of tubes and a patch kit, and three water bottles, and food, and a CO2 inflator, and an allen set, and a phone, and mace, and tire levers.... It gets out of hand pretty quickly. Since I live in a rural area there are no stores to get water(I am not filling my water bottle at the sheep trough) or food so I have to carry everything I may need on a ride.