^^^ this is a common misconception. I have made posts about this previously, but will do so again here for the sake of clarification.
Especially with large vehicles such as NPR/NPS, Mercedes Sprinters with 6" of wheel travel, OKA, MAN TGM, Volvo C303 and the like, basically anything bigger than a Polaris RZR, the ability to crawl, is invaluable. You do not want 5 - 8 tonnes flopping or bouncing around or sliding out of control. You want everything calm, smooth and very controlled, with plenty of time to react if something goes wrong.
There is less stress placed on the drive line, less damage done to the trail, more reaction time provided and fewer white knuckles from your passengers. Many who make comments such as, "I am not rock crawling, so I don't need low gears." have never ridden in or driven a deeply geared truck or buggy. The difference is chalk and cheese.
A Jeep JK Rubicon with a manual transmission has a crawl ratio of 84:1, while a USDM Sprinter has a 'crawl ratio' of about 25:1. I have ridden in Toyota trucks, 4Runners (Surf) and buggies with well over 200:1. It is astonishing what the vehicle will literally crawl over or up, with no effort whatsoever, even without diff locks, throttle input or brakes being used.
In the video below, the incline is quite steep, but I have seen MANY vehicles with "All-Terrain" tires and open diffs get stuck on wet grass, a muddy road or at a water bar running across a trail or track. Please watch the videos linked below and pay close attention to the speaker/host, the conditions and the text on the screen.
Note: this is NOT difficult terrain, yet the truck is hampered by AT tires, poor articulation, open diffs and high gearing. Whaddaya know, it's just like most SUVs, AWD vans and nearly everything this side of a Unimog.
The latter part of this video provides ample evidence for why "off roading" has been given a bad name and in many places, is simply banned. Having owned, driven and ridden in both "types" of vehicles, crawling up obstacles that are impossible to walk up, lots of gearing, slight throttle inputs, controlled and calm are certainly the way to go.