All of these are issues that are suited to ALL parts of the body. If something heavy falls, shouldn't I be wearing shin pads? If someone steps on my toes and I am a woman just wearing a slipper shoe, its not going to stop anything as well...perhaps we should all wear steel toed boots?! I have gotten my foot stepped on MANY times, as I normally wear opened toed sandals, and though it hurts, I have yet to break any bones. People usually have a problem with unkempt feet, but that would be a problem with unkempt parts of ANY body.
You are in an aisle seat and something heavy falls off a meal or DF cart?
Another particularly heavy pax (with shoes on) steps on your toes as you are passing in the aisle or waiting in line for the washrooms. I've seen that happen in a line for ice cream at a beach and heard the crunching noise of the toe bones. That poor girl was in agony and was screaming uncontrollably...horrible
There is some broken glass on the floor if someone has dropped a glass or crockery and the FA's (or cleaners if a previous flight) missed parts of it?
An FA or fellow pax spills some hot coffee or tea on your foot.
There are 4 reasons - took me all of 2 minutes to think of. Apart from that, it is truly disgusting to go into the lavs barefoot or in socks with what is usually on the floor after around 30 minutes of flight.