Beats the shit out of me (pun intended) why people can't leave facilities as they found them.
If you make a mess, clean it up.
How difficult is it to flush the toilet or give the seat a quick wipe if you've left something on it?
Having said that, most toilets I have the misfortune to visit these days have so obviously not been cleaned properly since installation. Do the cleaners think that flushing a toilet and dumping some disinfectant in it constitutes cleaning? If you're paid to do a job, do it properly. I'm the first to admit that people are pigs, and it's not a nice job being confronted with the state some people leave them in, but the ones that are not inclined to be clean certainly won't be even slightly guilted into leaving it clean if it's dirty to start with.
I HAVE to use disabled toilets and I have a condition that could leave me quite ill if I get a bladder infection (I use catheters and need to be clean). The amount of "shy shitters" who use the disabled loo just for a dump and then aren't fussy about flushing or have shit all over the seat from presumably hovering is shocking. I HATE using public toilets because I rarely come across any that are passably clean.
Oh, and beware visitors to your home, too... I thought I had a leak until I saw urine dribbling under the seat and down the outside of the pan onto the floor. Thank you, Mr Tradesman!