People at MIT who don't wear shoes

So I've been studying in the Student Center at MIT for Step 2 every day for the last three weeks. I have a week to go before my exam. Among my study-mates is this blonde girl who sits diagonally across from me every day who doesn't wear shoes. Now I know this is MIT and I know it's "normal" for people to not wear shoes, but honestly, that is just unsanitary. I mean, there is a reason stores and restaurants have signs that say no shoes, no shirt, no service. It's just disgusting.