Performance dogs are insanely high energy, that is desirable. Just because it's not what you look for in a pet does not mean it doesn't make a good pet for someone seeking those traits in their dogs.
This.
Like Emily said too, most people that are drawn to and get these dogs aren't looking for a the typical definition of a good pet. They want a sport dog, the want that energy and they want a competitive dog where they have some guarantee about the dogs ancestry, ability and how it's going to turn out.
But then again, I have no real issue with cross breeding to make a good pet if done with the proper health checks, proper temperament (and proving said temperament), dogs are cared for and if there is a market.
There is a void, sport dogs are filling it. I don't really see what the problem with that is. Lurchers, Alaskan Huskies, many many ranch dogs and all number of hunting dogs have been bred like that forever.