Alas, the stores aren't doing it just to be mean. They do it because of what some people (homeless or not) *do* to (and in) restrooms.

Everything from shoot up (and leave needles laying around) to use them as "bath" rooms, to leave incredible messes.

All of which make *customers* decide they don't want to use the business and (and, often cause large extra costs for cleaning and for having to inspect far more often (which takes employee time away from other things).

Some of those are the same reason restrooms in parks are closed or only open limited hours.