Why do we have to import 20K keywords when we know that they will have low search volume and will need to be deleted? Isn’t this a waste of time?

This is a way to get every possible combination of KW out there (We wouldn't teach it if it were a waste of time). The only waste of time is asking if what we teach is a waste of time. If you want to challenge what you're learning because you don't understand why we do things the way we do (even contrary to Google's advice in a lot of cases), then we suggest using more friendly language. Such as: "Help us understand why we need to do this" as opposed to "Isn't this a waste of time?".

We do welcome questions, we just don't encourage negatively framed questions. It's a mindset thing that we make everyone aware of.