Public Washrooms are there for if you need to go, so I use them for that very purpose. Where I live, unfortunately, the washrooms are almost never clean, so it does get quite disgusting sometimes.
I'm originally from Vancouver though, and there, it is a mixed situation. I find restaurants and shopping malls generally have well clean and maintained bathrooms, while practically everything else (especially gas stations... ew) has an extremely dirty and revolting bathroom. I guess though, if you gotta go, then you gotta go! I just prefer it when I don't have to walk into the stalls at school and see that somebody left their breakfast in the toilet. Nobody really wants to see that. Unfortunately, the toilets at my school are motion censored. In case it doesn't flush, there is a button one can press that makes it flush, but most people just walk away, and sometimes it doesn't pick up their movement.