I have occasionally driven a few hundred yards (e.g. from the local shop to home) without putting a seatbelt on, just for the frisson of excitement. I can report that this makes me really, really careful about how I drive. To play devil's advocate, maybe they should be optional for the driver only?
Also, unlike seatbelts, cycle helmets involve considerably more discomfort for the user. For me, the chin strap is the worst thing since pressure there aggravates my asthma, but there's also:
- heat in summer
- inability to choose appropriate headwear for the climate; you can't fit a woolly hat under one, and strictly speaking you're not supposed to wear a cap or Buff either
- weight, which is a big issue on a long ride when you are prone to fatigue and neck pain.
Fortunately the UK government has realised that wearing rates are too low to consider enforcement*. Jersey presumably has few voting cyclists, and more helmet-wearers anyway.
*which is why wearing a helmet is voting for compulsion according to the government's twisted logic, whether you like it or not.
http://www.peeble.com/bikes/letter1.gifhttp://www.peeble.com/bikes/letter2.gif