Shoes (mis)shape your feet! Almost all closed shoes and even many sandals that have straps across the toes will push those toes together to some extend. Women's shoes are especially bad, it's next to impossible to buy women's shoes that are not too narrow and won't push the big toe out of its natural alignment, but even men's shoes will usually push it out of alignment somewhat. I assume we all know high heels are unhealthy; but even a relatively low heel of half an inch or less will change the line of spine/knee/foot somewhat. Most of the 'supportive' foot beds not only don't work, but they even do some harm, although it isn't anywhere near as bad or as obvious as the 1 1/2 inch+ heels. Closed shoes are also breeding ground for all kinds of bacteria & fungi; while many people believe going barefoot is nasty, and yes of course we do step in lots of stuff that's infested with bacteria and all sorts of things, but stuff like that *grows* much quicker in the dark, damp and warm environment a shoe provides. Shoes allow people to blunder through life oblivious to their surroundings. Barefoot people usually are more aware of the ground they walk on; even though my feet are tough enough I rarely if ever divert my path when there's glass laying around, I still notice it. I don't have any proof of this but I think if more people went barefoot there would probably be less glass, dog crap and litter on the trails and sidewalks. Personally, I also like the various surfaces I encounter when barefoot; I often compare wearing shoes with wearing dark sunglasses all the time. Most people wouldn't want to wear dark sunglasses all day, every day; they'd miss all the color in life. I don't want to miss all the different things I feel underfoot! But that's a personal preference and it's not actually harmful to do without.