why Rust doesn't have a common interface for Integers ?

By reading the documentation, types such as u8, i8, u16 and so on have more or less the same methods and thus they have the same behaviour in the methodic sense, even if they work at different sizes.
Since Traits should describe common behaviour why there is no Integer trait or something like that ?
I mean I understand that std is supposed to be super slim and efficient, but introducing such a trait doesn't seem like the end of the world.