I’ve been doing it for years, you get used to it quickly. Walking on the cobblestones feels good with or without shoes, and I think it probably strengthens my feet and lower legs.
About ten years ago, I started noticing shoes for sale that had thick rocker soles – to mimic the uneven surfaces the Masai people of Africa walked on. The shoe makers claimed it created a healthier way to walk, just look at all the lean and fit Masai, they said.
Also, tradition Chinese medicine apparently has recommended, for many years, walking on cobblestone paths solely for the health benefits. I’ve read about lots of paths in China, constructed of river stones set into concrete, that are there to walk on just for health reasons (as opposed to trying to get somewhere).
I think it’s common to have these paths in the public spaces of large Chinese cities for folks to use. It’s sort of like gravity assisted accupressure massage for feet. Claims are made of lowering blood pressure, helping balance, and reducing frailty in the seniors.
Some people are pretty serious about walking on uneven surfaces. I stumbled upon a company selling cobblestone mats you can roll up and put away after your “workout.”
It’s hard to say how beneficial walking on uneven surfaces is, but I think there’s something to it.