... I'd also wager that well over 90% of the trails in any state are passable without even thinking of lockers...except maybe Alaska. ...
Maybe, likely, but I haven't wheeled all of the states to know. Most of the named, popular, destination, type routes are well groomed, if that and web wheeling is what you are looking for, lockers are good sig line filler. Some of the more challenging routes can be done unlocked, with lots of tire spin, digging holes, taking the strap, higher likelihood of damage, etc.
Most of the wheeling I do is for the Forest Service, one of our tasks is to run/inspect all of the routes (open, closed, otherwise) in Tonto, so ~4500mi of routes. May not seem like much, but we have often gone out, beat our stuff all day and only added 5mi. Often have no idea what we are going to find, so don't bother showing up on those days without at least one locker. On those days we have found some of the best stuff.
... And as Christo reminds, they are not a panacea; they can get you into the sort of trouble you'll still need a winch to get out of.
Oh boy, again,, I'm doing it "wrong"! Often put my rig in harms way, often in remote locations where no one has been, maybe in decades, and don't have a winch, the shame of it all!

We recently took the head of engineering for Tonto out for her first time in a 4x4, went on a relatively challenging route. As part of the debrief, she mentioned; I was watching didn't see a rig spin a tire all day, do you know how huge that is! Started the conversation about ground pressure among recreation types, how horses would be the worst, and big tire SUVs could be the least damaging. Properly prepared, locked rigs, with an operator that knows how to run it, can go amazing places without spinning a tire.
Fully agree on the route damage thing. If you don't think that soil displacement, erosion, silting, dust, etc, is a huge factor in our future OHV privilege, you have another thing coming. IMHO, lockers and knowing how to use them, are part of a well prepared rig, a commitment to lands stewardship and our future OHV use privilege. We are working with Tread Lightly on a new education, signing campaign and this is a big part of it.