There are a lot of scenarios - that don't involve a ruptured tank or line. Just think about if you happen to tip the car over on it's side - you're in a ditch. Gas starts to pour out of the carb, gets on the exhaust, fire starts. Meanwhile your fuel pump (depending on level in tank, where the pickup is, etc) - keeps pumping fuel at a furious rate to the carb. And - as the car is on it's side, the float assembly in the carb is probably not stopping the fuel from pouring in . . . and right out the top . . . making a HUGE fire. All the while, you're hanging from your seat belts!
