Why do we need Rigidbody in Unity

Question

I'm integrating Wwise for Unity, and I already stumbled upon some mentions and hints of "you need to add a Rigidbody", at least for some functionality? It's not clear to me why that is necessary. To me understanding a Rigidbody adds physics to that gameobjects, like gravity etc. But I don't need that for my game - why does Wwise require it, and for what?

Hope you can help me shed some light on this!