There's a niche group of people (particularly electronics distributor FAEs for some reason) who have them for the same reason many people own F150s: because they like to look like they work in that sort of environment.
I’ve met people who used business rugged as daily drivers, they’re somewhat less hostile and still rather nice: spill proof, hotswap battery, handle and strap, not as solid as the fully rugged but lighter and better looking.
Still expensive as hell new.
I use it as my "outdoor/garden/workshop" laptop that I can display CAD drawings on and stuff like that without worrying about getting wood splinters in it, or as a juke box/internet lookup-thing/spreadsheet when I work on a semi truck I sometimes drive (not for work though, purely for fun).
It does also double as my backup laptop in case the XPS13 I use for freelancing ever falls off the table or something, but I don't really see that happening anytime soon.
Granted, most of this I could just as well do with an old T-series Thinkpad, but there's something to having a carrying handle on the thing and being able to pull it off its keyboard base. Also, COM ports.