Because function overloading is conceptually a missconception. Logically if we assume that function name is describing a behaviour, there is no reason, that the same behaviour may be performed on two completelly independent, not simillar types - which is what overloading actually is. If there is a situation, where operation may be performed on set of types, its clear, that they have something in common, so this commoness shouold be extracted to trait, and then generalizing function over trait is straight way to go.
I'm just curios about your sentence:
Could you point such a situation?