But your observation is valid, their isn't too many of them. I also shoot an old Ithaca/SKB 500 O/U, and like it about as well as the 85. Bot no chokes for it, only mod/full. Still working on getting it choked at some point.
I used to own one in a combo form. Never fired a shot through it and got rid of it so I don't know much about them other than the people I see working on them at the range. I know a guy at my club who has a bag of parts and it seems he is always digging in for someone.
There are also some folks who never have a problem but for the most part those guys don't give them heavy use. They certainly would not be my first or last choice.