Ok. Forget the stinky lav.
Ever check the seat back pouches after even one leg? Ever look at all the dried face butter on the windows that won't even scrape off? The crusted carpet? Guessing the lunch 4 other passengers had on the tray table in front of me is always a favorite game too.
I deadhead in the back of our planes all the time, and I used to commute on Delta, NWA, and AirTran to DTW for years. What you're describing is a rarity, not the norm. Are the planes completely spotless like I'm sure you have to keep your planes for the rich a$$holes that you fly around? Of course not. Our planes are flying 12 hours a day with 45 minutes turns. Keeping them spotless is impossible. But in general, they're in pretty decent shape.