Mercedes has been using full selectable lockers in the Unimog since day one in the 1940s. Then mercedes had lockers in the g-wagon in 1979. Toyota offered full locking diffs in the fj60 in the 1980's and the fj80 had optional lockers in the 90s. Mitsubishi montero's had lockers in the 90s as well. That's really cool that jeeps are reliable driving on hard packed roads here in North America. Does it matter where I live? I drive a Toyota knowing that if it will last years of hard abuse overseas it will last even longer here.
"I ask, sir, what is the militia? It is the whole people, except for a few public officials."
— George Mason, in Debates in Virginia Convention on Ratification of the Constitution, Elliot, Vol. 3, June 16, 1788
Was a Unimog ever a mass produced civilian production vehichle capable as a daily driver? Jeeps have always had aftermarket support and a cheap 150 dollar Loc-Rite could be had and installed in a couple hours if need be back in the day. Lockers aren't the be all end all, it's the overall blend of everything and that is approach/departure/gearing/horsepower/torque(in a good usable range) crawl ratio, flex and the way the suspension works, ground clearance. Take a Mitsubishi Montero with IFS against a Jeep (especially a Jeep sway bar disconnected) and you will need a locker to make up for that tire up in the air. The Jeep will most likely still have tire contact patch on the ground.
What makes you keep bringing up "hard packed roads". southwest America has steep loose rock, sand, mud, Mud and bogs, other part of the country, snow> Is the US the only place in the world with paved roads?
I ask where you're from , what country because I think it's relevant. A customer at work has a 1979 CJ7 he bought brand new and has been a customer with us since day 1. He has 380,000 miles (over 35 years) and has never done anything more than routine things like a clutch, a water pump, some clutch pedal bushings, etc. It's an AMC 304. How is that not any less reliable than your Toyota? Terrain is terrain. "overseas" is not some magical fantasy land although it seems to be held in higher regard by you from what I gather. My thoughts are dirt is dirt. Vehicle abuse can be had many way from the kid doing nuetral drops daily in his jeep to revving a stock 29 inch wheel Jeep cherokee at 5000 RPM trying to go where the 35 inch tire Jeeps go to a Toyota carrying a troop of militia at 40 mph over bumpy roads, it's all the same.