OK, Thank Y’All. I mostly shoot privately so haven’t seen one of them. Only been to 1 Public Range near San Antonio.
As someone else noted it’s so you don’t have keep the eye shut and avoid that strain. I’m right handed and actually patched my good left eye forcing bad right eye to do more work, Over time, right eye improved somewhat from so doing.
i used to shoot High Power in a past lifetime, now i’m 30% blind(glaucoma) in my non-dominant eye but can “almost” get 20/20 corrected in my dominant eye and can’t wear contacts so i’ve been out of it for a looong time