Economic downturn. This stuff happens all the time, just ask your local dungeon developer. Or don't, because those guys are mostly jerks.

The ground might be softer in one direction. There may have been something worth mining out in a specific direction. Of course this only occurs orthogonally in the real world :) The main point is that with mining a tunnel is the natural structure and rooms would be unusual.

An empty hallway is great for storage and requires much less support than building out a room. It could also be explained by venting or similar that might not show up on a map.

"Gettin' ready to carve out the Master Dining Hall and what do we find? It's smack dab against a vein of mithril ore. You know what happens when you start digging mithril, right? We ain't doing that for no union scale!"

I used to work at the old IBM buildings in Austin; there were a few halls that went around a few corners only to dead-end. With a bunch of spare desks and chairs piled against the end wall.

Maybe humans wouldn't, but what about goblins? Orcs? What about dwarves digging exploratory tunnels, or following ore veins?

Maybe its for accessing utilities/maintenance.

Maybe it's an old broken passage.

Yeah, I wasn't entirely happy about these.

The random tables allow a corridor to end in a false or secret door (or stairs, but I stripped those out). So by the same logic, a corridor must be allowed to 'stop' or a dead-end would always mean "trap/secret" to the players.

But as others have said, it's not entirely unrealistic ;)

Well, almost no one. :) Sarah Winchester had such things built, with doors and stairs leading nowhere.

https://en.wikipedia.org/wiki/Winchester_Mystery_House

Ask the people who've been involved with the 2nd Avenue Subway about that...