you could, but the connotations of master/slave have been integrated heavily over the years, and changing it willy nilly doesn't really accomplish much since we're talking about moving electrons through wires, or light through glass. So i don't think anybody really cares about it at the end of the day.

Realistically though, very little designed architectures these days operate on a master slave meta. At best there's one "primary" and several "secondary" or "follower" nodes behind it. Or some kind of democratically elected process for handling that.