I've noticed in previous postings comments regarding wearing of seatbelts in private vehicles all the time, but not in a fire appliance.
Well, I'm guilty as well!
MFS does stipulate that they must be worn, but I haven't noticed too many people in Metro or Country doing it.
Our front running appliance (Scania) does have BA seats and if you have put a BA on, the shoulder straps alone would probably restrain you if you hadn't pushed down on the lever to release the set.
All BA seats do have retracting seatbelts, but crews find putting them on with an airset a bit of a tangle.
I suppose if anything happened and you were't wearing one, it could be detrimental to an injury payout, but who knows...........