Some folks don't have the luxury of being able to get their dogs out a lot, so the dogs feet never really get toughened up.
There are some places out west that have porus basalt which scours feet raw, or worse, volcanic glass.
On top of these, we get those damned longspine cactus that are really a bad deal.
I used to run my dogs after Huns and Chukar and usually their feet were conditioned enough.
Lots of bagbalm at the end of the day for them to sleep with glooped up feet seemed to help. I saw a guy had his pointer (dog) out too long and had to carry it back slung over his messenger bag. Poor pup.