What happens if the float hits the bottom, electrical short? No, really.
The world comes to an end!
More seriously, when modern fuel evaporates, it leaves a gummy substance which makes a great glue. Allowing the float to hit the bottom of the bowl allows the "glue" to affix the float to the bottom of the bowl, and when the owner attempts to start the vehicle, the float will not shut off, and fuel goes all over the engine.
Jon.
