You can compare pest removal to whatever you want but if you just let them roam around they leave scent trails that bring other pests to the area. One animal might not get in but a pack of them can do some real damage. Protection involves more than just putting more and more fencing up.
A pig is a really nasty animal with a long list of diseases it can transfer to humans, you don't hear of anybody turning a plate of bacon down.
And yes there is a furbearer market. I can remember back in the 80s getting $25-30 for a coon pelt. The bottom fell out because everybody and their...