I shower twice a day and always wash my feet, often scrubbing really hard. During the summer I wash and scrub my feet more often than that. These days I’m usually wearing Ufos flip flops so my feet are exposed to all sorts of dirty stuff.
I agree that it’s pretty gross that a lot of people don’t wash their feet. That’s probably part of why smelly food fungus is so common.
That being said, foot fungus can be contagious, I got a really nasty one from some slippers I tried on. The only time I’ve ever had a problem with anything like that. It started with an itch, turned into a horrible odor that got into all my very pricey running shoes plus all my other shoes, was making the skin peel off the tops of my feet. And I was washing my feet and shoes all the time. I tried all sorts of over the counter stuff, nothing really helped, then one day I was cleaning my very old shower grout with bleach and accidentally blocked the drain and was standing in diluted bleach solution. That night I noticed my feet didn’t feel as bad so I started soaking my feet in a weak bleach solution. That solved the problem, thank goodness. I did have to throw away all my shoes and I wore flip flops for about 6 months til I was sure it was gone.