I think it may be more a question of how clean the patron is. If they tend to walk around public places with no shoes on, one might imagine that their overall hygiene may not be particularly good.
Most likely though it's a health and safety policy - sharp things on the floor, etc.
I'm a fairly square, non-trouble-making, shower-positive individual who loves going around barefoot. I might think Tesco is the wrong place, but I wouldn't assume anything about a barefooted person.
Most likely though it's a health and safety policy - sharp things on the floor, etc.