Because PhilIsStupid I currently have scars which are healing.
Interesting mechanism : blood is everywhere in the body. It contains one kind of agent, which, on contact with the air, starts to coagulate into a dry / protecting crust. When you're cut, almost certainly some blood will come out, and then the coagulation process will do it's work, sealing the wound, keeping out bacteria, protecting the healing wound from further damage through grazing other surfaces etc.
This functionality is superimposed (FractalLoading) onto the blood supply. In fact, blood is a general purpose communication network, supporting not just this auto-protection, but the ImmuneSystem, various kinds of supply of nutrients and energy etc.