Please don't pay to use a pay toilet

For old/sick and poor people this is a real problem.

I just realized that my old relative avoids going to public places because he it becomes expensive when he needs to visit toilet frequently.

Toilets as public utilities where whoever keeps the toilet is compensated by the number of visits would be one good solution. Zoning regulation could mandate some amount of public toilets.

Why hasn't charging for toilets caught on in the US?

I suppose some places require a receipt for use, but still. Or perhaps, why do many places in the EU charge?

I've noticed that pay toilets in the EU are still disgusting.

Eh. I hope the comment about legality is supposed to be a joke/hyperbole. Otherwise agreed.