You can bypass them very easily, but in the event of an accident if say the return hose was ruptured but the engine was still running it would be pumping fuel all over the hot engine, and could result in a very nasty fire, with the occupants possibly burning alive in the car unconscious, is the main reason, the way I see it personally is it costs little to have it there, but it could save your life, it's disgraceful it was never fitted on some and ford should be ashamed of themselves imo.
tabetha