I read once that one reason is ADA compliance. Having a gap under the partitions allows space for the toes of wheelchair users to navigate, so the stalls may be smaller. DDG turns up this plumbing blog post which lists that among other non-obvious reasons: https://onepointpartitions.com/why-are-bathroom-stalls-not-t...

And a more authoritative reference here: https://www.ada.gov/regs2010/2010ADAStandards/2010ADAstandar... (Ctrl+F "604.8.1.4")

Do public restrooms in the US typically have stalls for handicapped people? That would require two to be built (one for each gender). Contrast that with building a completely separate restroom - you can only build one, and you can still have a smaller footprint on the "regular" stalls.

Yes. Separate rooms do exist but are pretty rare.

Yeah but why doesn't it go to the ceiling? I don't want to make eye contact with my pooping neighborhood when we both stand up. And, the smaller issue, why are there gaps around the door?

I've brought this up at my workplace as well and it isn't a budget issue in the US, it's mostly a lack of creativity or follow through from your office management team. Because more private, both in height and gap, doors aren't common in the US contractors aren't used to installing them and suppliers don't commonly carry them.

You can find them at suppliers in major cities but you have to rely on the persistence of your office managers to track them down and spend time on something that most people don't rally around or bring up in discussions. The compromise in my office was rubber strips that cover the gaps found in normal stall doors, those are easily bought and installed by anybody.

Lack of standards for stall doors (its probably not in the code so anything goes and I suspect if the door is closer to the floor it needs a more precise (expensive) installation.

Lack of code is also probably the cause of the randomness of urinal heights.