system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 Why are the front of a lot of city buses a flat square? Isnt that the least aerodynamic shape there is?

Seems like theyre so heavy anyway they'd try and save fuel.
gpt
A more aerodynamic shape would help fuel efficiency some, but not that much for two reasons. First, buses don't travel that fast and drag (air resistance in this case) becomes a bigger deal at higher velocity. 

Second, there are two different types of drag: drag from pushing air out of the way and drag from air passing over the surface of the vehicle. For a short car, there isn't much surface for air to pass over so pretty much all of the drag comes from pushing air out of the way. That's also the sort of drag an aerodynamic shape helps with. For a long vehicle like a bus, drag from air passing over its surface area is a bigger deal. There's still more overall drag on a bus from having to push air out of the way, but skin drag is a much bigger component than it is for cars. This makes the drag from having to push air out of the way in the front less important for buses.

Those are just reasons why an aerodynamic shape won't help a bus as much, though; they're not reasons to not do it. The reason buses are designed with a flat front is that it maximizes volume and a flat front and window allow the driver to see better, especially when turning. The increased space and visibility are more important than any small increase in efficiency from a more aerodynamic shape.

tl;dr - Buses benefit less from aerodynamics because of their long shape and they would be hurt by a more aerodynamic shape because a flat front maximizes space and driver visibility.

Edit: In response to the multiple comments saying that some buses go fast, we know that. But most buses do not and when buses are designed it's usually not clear exactly how they'll be used. And even for the ones that get on the freeway, the flat front is better for volume and for turning once the bus inevitably leaves the freeway.