Generally, they don't use them for anything. Kind of cyberpunk LARPing or something.

They actually have a purpose, if you're in a role where you need to interface with a lot electro-mechanical stuff of varying vintage though. Basically ends up being a pelican case with a fat battery, a small network with short patch cables for reconfiguration on the go, two SBCs running windows IOT and linux, a PLC + 2/3 I/O cards, a CAN adapter and some space for 6 inches of terminal block on a DIN rail. Then a keyboard + monitor.

Maybe not as sexy as some people make but it is a cyberdeck/briefcase lab and it will allow you probe most distressed machines without having to waste time running around for supplies or back and forth to offices.

The way many manufacturers are structured however, there is too much red-tape and osha for this to be a reality for a lot of people, at least in the usa. It does exist in some places though.