Calluses can occur from many different things. And just because a dog has callouses, doesn't mean their current home caused them, or that they weren't properly cared for.
None of my dogs have been "dog bed dogs". They slept on the couch, bed and/or floor - their choice. Some had callouses, some didn't. Tornado-dog is a contortionist. He will crawl under an armchair and nap (or look for things to steal) - seriously, he is 20.5 inches tall and routinely crawls under a chair with just under 7 inches space. The way he crawls, I won't be surprised if he develops callouses.
1975 American Clipper RV with Dodge 360 (photo in profile)
1998 American Clipper Fold n Roll Folding Trailer
Both born in Morgan Hill, CA to Irv Perch (Daddy of the Aristocrat trailers)