It is a woman thing.
For a gender that has on average at least 20 times more shoes than men, at the same time they like having bare feet and flip flops are the closest thing they can wear if they want a little cushion/protection/keep feet from street dirt.
Actually there is something even closer to barefoot than a flip flop. I don’t know what they are called, and the first time I saw them they kinda weirded me out. They look like a glove made for feet, complete with ‘toes’ instead of ‘fingers’. A woman was wearing them when I saw them.