There’s no need for master terminology there
Nobody said there is a need, you could call it foo or bar and it would still work. It just that master more accurately describes what it is. Main for example does not describe a derivative relationship, master does.
Also, master in this context is totally unrelated to slavery so I could also just as easily say that there was no need to replace the existing terminology either. It doesn't solve any real world problems of historic or currently existing slavery, and it doesn't make anyone's life better. The only reasons why it was done were appeasement and virtue signalling.