In EU, you have to pay to enter a public bathroom. But as return, the bathroom is kept clean (or at least that is the idea).

I read a story the other day how restaurants allowed free bathroom usage to tourists in Germany. This was paid by city council, and allows for a more pleasant stay of tourists. So they like to come and/or return. Word of mouth works.

The links say there are 25 of these restrooms in a city of over 850,000 people. That's about 1 per 34,000 people. They are described in the second link as being unreliable and gross, and people are suggested to avoid them in favor of private restrooms. This is not functionally different from not having public restrooms.

I believe that in California, businesses are required by law to allow people to use restrooms, but they try to avoid compliance and do whatever they can to keep homeless people away.

I don't think it's a fair calculation. SF is not uniform, neither is population, neither are locations of people that need public bathrooms. So just dividing number of citizens in the whole city to number of public bathrooms makes little sense. Center where population traffic is stronger and where there are usually more people needing those services should have more, while remote purely residential neighborhoods may not need them at all.

> I believe that in California, businesses are required by law to allow people to use restrooms,

They do, and I myself used them many times, but for a person who is looking, as said in parallel thread, "sketchy" and may have some trouble expressing themselves, it may be a different story. The reluctance of the establishments is also understandable - if the person makes a mess there, somebody will have to clean up, and odds are nobody but the person behind the counter getting minimum wage is there to do it. So, their reluctance to allow somebody who, in their opinion, is likely to make a mess to use their facilities is not hard to understand, IMHO.