I'm sure that's why dogs don't have those problems. Oh wait, yes they do. Furthermore, "natural" does not mean you have the capability to go anywhere you please without technology, "natural" means you have a short and painful life in a highly limited habitat. In fact, in a situation without shoes, man naturally.... invents shoes.
Just completed a flight to Florida, with a layover in Atlanta. I love to fly and walk the airport terminals barefoot. Atlanta is a great airport to walk, it's incredibly large and plenty of sensations.
I got flights barefoot many times. even in Japan. Almost never problems, just once in Bankok airport, in transit area, from Vietnam to Milan, a lady on duty told me I could be refused embarking by the crew, asked me to wait, but I put on a pair of under-shoes, socks with no legs (what do you say in english? in italian they are -fantasmini-, as -little ghosts) and all problems disappeared. I like spending most my holidays barefoot, lat year in Vietnam I was barefoot 23 days 24h a day.