system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How come passengers on buses or limos don't have to wear seat belts but the every day car does?
gpt
It all has to do with how much momentum a bus has compared to a car. Compared to almost everything else on the road, a car usually will have the less or equivalent amount of mass. So, if a car crashes into another car, a bus, or something even larger, the car will take serious damage and stop very suddenly, and has a very good chance of killing any unseatbelted passengers.

However, a bus is one of the larger things on the road, and cars are much more common. So, if a bus gets into an accident, chances are it will hit a car, and because the bus is so much more massive, the bus will plow through the car like it is practically nothing. So it's much less likely for you to get into a potentially fatal accident in a bus then it is in a car. Therefore, the rules regarding seatbelts are much less strict.

Tl;dr: Because busses are much more massive than most other things on the road, it is much less likely for an accident in a bus to be fatal. So the safety regulations are less strict.