This is props to a friend of mine, Tina. When we were both juniors, she started rallying with her sister on "my" court between singles and doubles matches. Barefoot, on clay.
For a variety of reasons I thought this - maybe from other perspectives simple act - wasn't possible and has stuck with me since.
Still I never tried this myself for ~25 years (!), mostly being blocked by the belief that due to the thin and sensitive skin under my feet, the coarse clay would quickly cause pain, cracks, and open wounds.
(I did try a few sessions when the FiveFingers came out, that actually went surprisingly well.)
As my left foot got weaker following an achilles tendon injury, I started looking for creative ways to strengthen it after the initial rest and recover period.
Even if it seemed risky at first, playing barefoot worked and did help. I was hoping for some re-discovery of natural contact, stability, and movement. Thankfully that seemed to happen.
Felt some reconnection to the brain aka increased awareness, and better usage and loading of the whole chain upwards. Before, I was consciously or subconsciously taking pressure off, and couldn't gauge the amount well.
I started on indoors on carpet, and eventually gave a few sessions on clay a go. Obviously sliding is not a great idea, however carpet-style footwork works pretty well. Especially if you're "just" rallying.
Indoors I even played a few sets barefoot - happy to provide takeaways later.
For now, thanks Tina for breaking down that barrier for me :) Maybe a little sign how constrained our thinking can be(come)...