yes because i mentioned anything about this.
seems its practical for cars and people for the most part follow it. seatbelts save lives is the slogan. you could easily retrofit the seats with a sensor that beeps like a car if the belt is not fastened while seated.
anyone not wearing a belt (passengers) at the bar or first class you mention should knowingly waive their right to compensation. otherwise they can sit in their seat like everyone else and fasten their belt for safety. diverted flights for defiance of rules just like there is with violence and abuse. heavy fines and bans would condition almost everyone to wear a belt at all times while flying....just like it does with violence and abuse.
as for staff they should have insurance provided by the airline to cover the risk and injury they might incur at work.