Take someone used to wearing stiff-bottomed shoes, and tell them to walk around barefoot on the street or on a forest trail. They’ll suddenly be intensely aware of the temperature and texture of the ground. Stepping on a little pebble will cause pain from sensory overload of nerves which have been carefully shielded for years. (Most people in developed countries can try this experiment out first-hand.)
For someone who is habitually barefoot, by contrast, walking around on very rough surfaces is no problem.
As some who used to walk around barefoot all the time as a kid, this effect is not due to habituation, but due to the skin on you feet becoming thick to the point that you are effectively wearing shoes. The more you wear shoes the thinner the skin gets. They other factor is you learn to walk differently such that you are more careful placing your feet on the ground to avoid sharp objects.
A big part of it is nerve/brain response, in my own personal experience, though sure, a different walking technique makes a difference too.
I started wearing mostly thin soled shoes a few years ago: simple leather moccasins, $5 Chinese canvas shoes, Vibram Five Fingers. (I don’t typically walk around outside barefoot.)
When I first started, if I walked barefoot, stepping on a tiny pebble was painful. Wearing thin-soled shoes itself let me very dramatically feel the ground in a way I didn’t when wearing stiff-bottomoed shoes. Now, a few years later, the effect is much reduced, even though the skin on the bottom of my foot is not noticeably more callused than before. I can notice how the ground feels if I pay careful conscious attention to it, but it’s not constantly in my mind as I walk around.
I think the walking barefoot -> calluses idea is exaggerated in popular imagination. I have a friend who does significant amounts of barefoot trail running, and frequently run barefoot on pavement. His feet are also not obviously more callused than anyone else’s.
I can say that to get thick skin on your feet you need to not wear shoes at all for long periods of time and walk/run lots over harsh ground. I would go the entire summer without wearing shoes and running around all day and it would take a month to get thick skin on my feet and it would still be getting thicker by the end of summer. I would start wearing shoes and within a month my feet were back to a more standard thinness.
You do retain the careful walking/running skill, but without the thick skin you can't really run effectively on gravel, etc.
For someone who is habitually barefoot, by contrast, walking around on very rough surfaces is no problem.
Same kind of thing here.