dung beetles and many other insects eat poo. I'm also fairly certain that some rodents will eat their poop to get more out of their hard to digest diet. I'm sure there's more.
Sorry, I couldn't help myself. The why's don't really matter but the fact is, a lot of animals do eat poo.
Opps, forgot about DUNG beetles! Gah!
Hermits really eat worm castings? Interesting.
To say that no animals eat waste was a bit harsh.
I stand corrected.