I would guess it's a safety issue, say you drop the pump handle and it's still held open by the device, pretty dodgy really! I know that the nozzle should be in the tank filler neck but there are plenty people out there who can create such a scene believe me! Also there's a chance of it sticking or people not stopping it early enough. In general I've found safety issues more relaxed abroad right down to the way people cross the road (challenging the traffic on crossings!) I know which system I prefer.