Well, he'd spent some time camping and drifting before Raylan picked him up, so he understands. There is a freedom to not being tied down to a place. Though lately Doc has found freedom in being able to say he is staying someplace and not feel tied down by it.

"Alone?" he inquires further. Not that he's interested in whom she wants to spend her nights with, but it is not and has never been a good idea to stay alone in Mathias.