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Dracula5555 The proper use and ranges of motion, etc., of body parts is always important. If the only alternative to being barefoot were heels with a 5" height difference between heel and toes, going barefoot would be the far safer, better alternative.
If you are "hearing" that from people who are always/mostly barefoot who proselytize for it and only have anecdotal, non-scientific info...then it's the opinion of those who "drank the Kool-Aid".
It used to be known as the #1 cause of ringworm [in humans] in the [American] South"...look that up to see what that implies.
There's enough actual crap, urine, dead things, and garbage, litter, etc., to walk through. Add to that bits of metal and glass (which should have been recycled) a d constructions debris--nails and other fasteners; sharp bits of broken-up concrete; possible rusty rebar, posts, beams, fencing embedded in concrete... All that makes sharp rocks seem like a much better risk.
And critters...in some areas, snakes. I've seen poisonous snakes beyond where they were "supposed" to be.
But in MANY areas, ticks are on the rise as warm weather moves North. More access to you means a better chance of Lyme disease.
Go barefoot all the time if you want, but be smart about where, when...be careful!