https://www.washingtonpost.com/news/parenting/wp/2016/02/29/why-kids-should-go-barefoot-more-and-probably-adults-too/

During an unseasonably warm day this past winter, my husband and I
walked with our three boys to the playground down the street from our house. The
sunshine was toasty and the boys were quick to take advantage of it. As soon as
we arrived, all three of our little boys immediately shed the light jackets they
had been wearing, along with their shoes and socks, and took off, small bare
feet pounding and bouncing on the playground’s rubberized soft surface. They ran
fast, climbed easily, using their feet to wrap around the poles they scaled,
clearly delighted. It wasn’t long before a few other children at the playground
caught on and attempted to remove their shoes and socks.

One major benefit of allowing a child to go barefoot is that it strengthens the
feet and lower legs, making the body more agile and less prone to injury. It
also enhances proprioception, the sense of the relative position of neighboring
parts of the body and strength of effort being employed in movement. In other
words, going barefoot helps a child develop body awareness. Geary explains that
the nerves in our feet are sensitive (the sole of your foot has over 200,000
nerve endings– one of the highest concentrations in the entire body) for this
very reason; they make us safer, more careful, and better able to adapt to the
ground beneath us. When barefoot, we are better able to climb, cut, pivot,
balance, and adjust rapidly when the ground shifts beneath us, as it does when
we walk on uneven terrain, or anything besides concrete and pavement.

And finally, going barefoot is a joy to the senses, especially to young children
who experience all the newness of the tactile world around them. Think of the
relaxing feeling of walking on soft warm sand at the beach, the refreshing
feeling of cool dewy grass in the early morning of a summer day, the feeling of
slippery wet mud squishing between toes in the garden, the feeling of the rough
bark of a climbing tree, the surprise at the splash of a puddle underfoot. All
of these sensations are available when we allow our children to experience a bit
of shoe-free time. Perhaps you should join us and kick off those shoes at the
playground and in the back yard. Enjoy your feet and what they were made for.