If you believe as I do that the xenomorphs are war toys, biological weapons, then they never really existed in the wild. If some escape and a queen begins to breed outside captivity, that constitutes "wild," but it would be like a pair of tigers born in a zoo escaping and then having cubs somewhere out on Long Island. Zookeepers would prefer to capture the big cats and put them back into enclosures.
I suspect that most people come to the franchise to watch the movies or read the books because they are looking for a certain kind of adventure. Part of that is seeing humans go up against the aliens, and the easy way to do that is to have a supply of the critters in captivity close to where the humans are. Turn 'em loose, instant conflict.
The social structure of the xenomorphs is ant-like, in that there is a queen who lays all the eggs, and a lot of drones, and their primary drive seems to be to find hosts and continue their life-cycle via chest-bursters. Any planet where a lot of them are running around loose is going to be a constant struggle for potential hosts, and dangerous. You'd need a good reason to go there if you knew what was what.
Remember Ripley warning the company that it was a bad idea to go bug-hunting? But there were other forces at play, and they went.
Anybody who would go to a whole planet full of the critters would need a really good reason, or a death-wish.
Somebody steps into a cage with tigers is taking a risk, even with a gun, chair, and whip. That's why people go to see the show, that chance that the guy in the cage might get et. It happens.
A guy does it for money gets mauled? Too bad, he knew the risks. Somebody who gets into the cage because his girlfriend or daughter is out cold on the floor and he's trying to save her? That's a different story.
