Because it might not have the functionality you want. Things aren't black and white, but one solution might be closer to what you need than jury rigging something yourself.

> Quality is also debatable. For a WM productivity is far more important than quality.

We'd need to agree both on "quality" and "productivity" here since those do not have well defined meaning. For me when it comes to software that helps me be productive, quality includes it helps me be productive, so there isn't a relationship where i can say that one is more important than the other since one implies the other.