I often decline as long as possible to use public toilets for a few reasons. In most cases, I am in a store in the early hours of the night (midnight-2 am) because I hate crowds and enjoy being able to look around without snot-nosed kids screaming their heads off or rude people running in to me. This presents a dangerous situation because usually the bars let out around 2 or 2:30, and drunk people apparently like to hang out at 24-hour stores to sober up before work in four hours... as the bathrooms at Wal-Mart and K-Mart can attest to. Not much worse than hearing a drunk moaning and groaning that early in the morning while dumping a lump, usually within three feet of a toilet.
What created the first problem with me and public bathrooms was elementary school. There was a graffiti problem when I was in the second grade, so the principal decided it would just be best to REMOVE THE DOORS from the stalls in boys' restrooms all over the school so no one could hide in one and write misspelled swear words and crude caveman-like drawings of boobs and penises. So I was in the bathroom one day for a potty emergency, and I was alone for all of about two minutes. Then three other boys showed up and stood outside the stall, watching me go to the bathroom... when you are 6-7 years old, you aren't sure how to handle a situation like that. They didn't say a word, just stood there and was watching me like some sort of pooping science experiment. So I attempted to cover myself as I stood up and hitched up my pants and left. I reported them, but I was told that if I am uncomfortable going to the bathroom at school that I shouldn't do it in the future. Yeah, it's my fault they served chili for lunch. I have not been able to use a public bathroom for anything more important than a pee in well over twenty years now.
And why is it that even when I do have to take a whizz at Wal-Mart is some guy always taking the poop of his life in there?! And he's always the "uhhh" guy too... we don't need you to announce the next bomb to us outside of your stall, buddy. But there is always some guy in there on a cell phone, usually the next stall over from the loud dumper, who just talks louder when the poop machine revs his engine for another evacuation. Whenever possible, if the door leading out locks, I lock that mofo to keep people out. It might be against store policy, but I don't work there and there usually isn't a sign that says you shouldn't lock the main door.
I would guess that pay toilets are probably the worst of the worst. If you had to pay each time you needed to take care of business, I'm sure you'd do what you could to get your money's worth every time.
I was working a blue collar job that went through a temp service for a while to fill in the summer gaps in staffing. There wasn't a big screening process that year for some reason, and we managed to get a bunch of drug addicts and even a steroid freak. One of the guys nicknamed Sherm had a bad habit of thinking it was funny to pee on your feet if you were standing next to him at the urinal. What makes people think this is funny? I realize that being a bathroom attendant is probably a horrible job, but a very needed one in EVERY public bathroom. They are as important as a good 48" exhaust fan in there, too!