I think there's a noticeable fundamental difference, in that humans have a natural walking pace. It's physically uncomfortable to slow your pace too much. They do both have the mental discomfort of being forced by a stranger to wait behind them, breathing down their neck.
On the other side, a slow walker often is walking slow because they naturally walk slowly. A slow driver often is driving slow because they decided they wanted to drive slow. (Or in either case, they're slow because they are distracted.)
On the other side, a slow walker often is walking slow because they naturally walk slowly. A slow driver often is driving slow because they decided they wanted to drive slow. (Or in either case, they're slow because they are distracted.)