Step 1: woman goes into public woman's bathroom.
Step 2: even if they've somehow never been before, "Wait, a woman's been in here. A woman has used this." They know what that means.
Step 3: hover.
I wonder if there's a selection effect. I wonder if most already know the following advice: plan not to use the public restroom. Find a way to avoid it. Result: only the most mindless segment of the population ends up in these places.