In some enlightened European countries like Sweden, many swimming pools require that people remove their shoes before entering the changing room area. This makes sense as the damp on the floors makes a nasty mix with the dirt from shoes and people will be bare foot in there. I have heard that this can be awkward for people who want to weat flip flops in the changing rooms for fear of Athelete's Foot.
I remember a holiday in France when I was 16. You were supposed to remove your shoes before going in the shower block at the campsite to avoid mud getting in. Regrettably, I found this irritating at the time and did not always comply.