Yeah, it's the Absurdly Spacious Sewer trope all developers fall back to when they need to pad their game with something easy to design. In fact, you'd be hard pressed to find a RPG, shooter, blobber etc. without a sewer level. It's simple, really: create a confusing series of identical-looking dark hallways, and populate them with enemies. Same as with most dungeons. The overworld is more difficult to design (since it would be weird if everything looked the same), but it's so much more valuable for it.

No I haven't but I'd love to give it a go! I didn't even realize that turtles in time had an arcade version. The only arcade tmnt game I've played was the one that starts in the burning building with the bowling balls coming down the stairs. I did get MAME running, specifically to check out the arcade version of golden axe, so I could try to get turtles in time working on it.

I liked the sewers in Baldur's Gate - Dark Alliance. Sewerwise DA even trumps the real BG games.