It’s not that they don’t know how a toilet is supposed to be used. It’s that they don’t like to go like that. I’ve been told that by people of MENA origin. They prefer to squat. It’s what they are used to and some say they cannot go any other way. So they stand on the toilet and squat. Naturally a lot of ... material ... doesn’t make it into the toilet bowl but ends up on the seat and some of it falls on the floor.
I saw a lot of that when travelling in certain areas.
Because of the mess, other people who would otherwise sit down, but who are desperate to go, have to hover over the toilet .... and they can make a mess as well.
I speak from experience.
In many places in southern Europe and in Israel two types of toilets are available ... the squatting floor type and the Western sit-down type. When this is provided you get a generally cleaner restroom, but it still stinks to high heaven because the squat toilets don’t “flush” as well.
In the Middle East you rarely see a sit-down toilet unless you are in a Western hotel or establishment. One has to develop strategies for going to the bathroom (one of them is to go as little as possible) and other strategies for keeping as clean as you can if you have to use one. I won’t go into specifics but there are measures you an take to minimize getting contaminated. But you have to have a plan.
That said, I’ve seen some pretty disgusting things in Western public restrooms, which I also try to avoid.
Must be hell for people with leg or knee injuries to have to squat like that. No disabilities acts in those places, I'll wager.