Actually parkour is all about overcoming obstacles and doing so in the fastest way possible.
Urbex is just a fancy way of saying exploring urban areas, and as you might guess parkour is by far most often done in urban environments.
My original point is parkour is ideal in abandoned places because you won't get yourself in trouble with the owners / keepers and not filled with people.
Also common sense will keep you safe in doing parkour anywhere.
cute
You could just as easily get in trouble with owners/keepers/police/whoever just by walking around there, why would you want to be leaping around the place?
No common sense would keep flooring or a beam or something from falling out from under you. Urbex is about urban areas, but most commonly is about neglected urban areas that have fallen into disrepair.
By all means, you can go do parkour in an abandoned factory or some stuff, but don't promote crossing these two activities to other people. The safety risk doubles when you're stunting and sprinting to get somewhere quickly, and to cross that with urbex is just nothing something that you want to risk. Like I said, do whatever you want to do, but don't suggest that other people do it. One or the other is exhilarating enough, stuff.