Most of my camping is done in non-bug season, so I have no desire to carry the extra weight of a bug net when I don't even need it.
Also, it's very difficult to make a quick exit with an attached bugnet. When I (rarely) get a calf cramp, I need to get up, standup, ASAP. Trying to find the zipper just increases my panic.
And then there's the animal issue - if I hear an animal in my camp I want to be standing on my own two feet ASAP. Raccoons, skunk, porcupines, squirrels, coyotes and deer will all pretty much skedaddle once you stand up.
When I do carry a bugnet, it's independent with shock cord bottom entry - very quick and easy to swing my feet out and stand up.