In quantum mechanics, the fundamental description is a wave function obeying the Schrodinger equation. But that doesn't help human beings in coming to grips with what the world actually looks like according to that picture. And so for a human being trying to understand how the world works, you also want to explain why it looks like wave functions collapse when you measure them. The Everett interpretation has no problem doing that, but that is an absolutely important step in mapping Everett onto reality.