Suspension of disbelief.
GF: I am LOST in a MAZE of sewer tunnels!
Me: Good thing you can’t smell them.
GF: OH MY GOD EXCELLENT POINT.
Me: Your poor character.
GF: It’s too bad they don’t make enchanted nose plugs or something. Or waste-repellant boots, because—seriously—you should see the “water” my character had to walk through.
Me: Ew. Sewage! …Do they have sewers in Tamriel? Or are they not up to that point of development yet?
GF: That’s what I was thinking! When is this supposed to take place? I would think a sewage/plumbing system would be too advanced…
Me: But in Skyrim they have sewers. Up in Solitude, at least.
GF: But Skyrim takes place several hundreds years later.
Me: Exactly. In Oblivion, it might be too early for them to recognize the importance of sanitation.
Me: …I can’t believe we’re discussing this. Go kill something with magic!
GF: …I guess the sewers were just a way for the developers to add more mystery to the game. I mean, the game citizens don’t even have TOILETS.
Me: Seriously, we can’t talk about this any more. Go slay something.
GF: Why? Is it bothering you?
Me: No, just, it’s a game. I don’t need to wonder about where the people in Bravil go to take a shit.