If you see someone sitting waiting for the bus, then the ONLY polite thing to do is to let them go first. As the bus pulls up you say "You were here first, and you go ahead". and then civilized people stop and wait. It's sort of like when you're waiting for an elevator - everyone knows who has arrived first and you just take your turn. And above that - you give the exiting people a chance to get off first, which people do not do.
There are benches at the bus stop for a reason, so you can sit and wait. I get to the bus early enough to sit and wait and others come running in at the last minute YOu know who was there first, and you should let them board first.
I actually like how some of the bus lines have a queue - I think that makes it a lot easier - you just get in line. But when there is no queue, make no mistake, people know which order they arrived in. And if you arrive and there are people already there, then they get on the bus first.
I assume you are referring to there not being alot of people waiting in the same area for the bus. If I walk up and see people sitting on the benches and the bus pulls up and there isn't a crowd of people that has formed with the people still sitting on the benches then I always step aside and let them go first. But if alot of people have shown up and the people on the bench are still sitting then I feel like it's their problem. I have also been at a bus stop at my hotel waiting and when I see many people coming we always get up and stand to assure we have a seat. I wish all bus lines had a queue, but the resort bus stops usually don't. When alot of people start showing up then no you don't remember who was their first.