While this isn't applicable in all areas, a rule of thumb could be "those who making money with the people which have to use toilets".
Anecdotal example: I'm living in an amusement district of a big German City. There are very few public toilets and most of the few are paid ones. So every weekend the whole district is smelling like a big bowl of piss, except in winter when the frozen pee of multiple weekends accumulate until there is the big pee-melt.
Why not making all those bars, clubs and liqor stores pay for the maintanance of free public toilets?