I normally try to be very cordial, but there is a reason you expect misses. I don't talk about theory. I'm talking real life experience. Ask all the guys I hunt with and have shot with. A scope level/anti-can't device is priceless if setup correctly. And a guy CAN'T tell if the reticle is perfectly straight using trees, etc. They lean. And what if there is wind.Ive been L/R hunting for about 50 years in the area of the country where it began. I can take you to many different camps within a few miles of ours where all they do is hunt L/R including names well known here. You wont be finding any scope levels and i doubt very much any wind meters either. What you will find is that (all) of them shoot from a bench of some type, and some myself included might use a small level when setting it up. Misses can be expected when shooting at an animal L/R especially where there are lots of trees having lots of branches. Problem with reading these post is that they are much to do about theory and little to do with actually doing it. Anybody who cant tell wether their reticle is canted or not maybe shouldn't be shooting that far.
We use a return to battery rest for our guns, which means you cant adjust the cant angle, so a level bench is more important for us. We sometimes just use a bipod also on the bench depending on the gun we use.
But otherwise a shooter should be able to straighten it out without a gadget attached to his scope he wont have time to look at anyway once the action starts.
You might not use them, but you are dead wrong that there is no advantage or use. If you're around sw Idaho, I'll happily take you out and show you.