If a semi-auto is used at a range- do you just leave the shells on the ground?
Shell catchers work on singles, but must be removed for doubles. Some clubs don't allow grounded hulls to be harvested -- it takes up valuable shooting time.
This brings up another topic: if you're going to shoot a lot of targets, then there is a high probability you'll reload. Autos and reloading are, at best, a marriage made in hell. That's one reason many folks prefer O/Us.