Why buses doesn’t have restroom/s but airplane does?

When I was a kid on bus/field trip, I need to hold this situation that I need to go to the restroom. So I urinate on something like plastic bag or plastic cup on one day. But at least when I feel vomiting, there’s paper bag on another day. If the person needs to go on restroom and go out on bus, then the bus leave and wait, however it pays you again when you need/want to another ride to another place but sometimes, they stop the bus to go to the restroom when sometimes the distance is limit far. So what’s the reason of it?
Answers

MS

Many buses do have restrooms - most charter buses and buses that provide long distance service do. But you can always stop a bus for a bathroom break - you can't do that with a plane.

sunshine_mel

You can stop a bus. You can't stop a plane.

Anonymous

Many buses do if they're meant for long distance trips. The reason is maintenance. Obviously when you use the bathroom, they need to put the waste somewhere and refill the water and things every so often. They can't just dump it on the streets. Airplane flights are generally a few hours, but the buses you describe seem like they're meant for shorter distances. Charter buses and greyhound have bathrooms usually.

bluebellbkk

Long-distance buses generally DO have a toilet on board. (I promise you, nobody 'rests' in them.)

drip

Schools use school buses for field trips. School buses do not need bathrooms as they are usually used for short time periods, Even a field trip ride is usually no more than an hour. Charter buses that go a long distance do have a bathroom.

Foofa

Some busses actually do have bathrooms.