Why does this plugin not use categories, rather than groups?

Hi ya,
So I can see no reason to have these plugins use groups, rather than link to the categories of posts/pages.

We can ONLY create groups when adding a subscriber, and if all the subscribers of a group are removed, then that group disappears.

This is very odd, and unhelpful.

And since you seem to only be able to add Groups with a new subscriber, then you have to create a fake new subscriber in order to have new groups.

Why not simply use the existing categories?

I can understand the use of groups to “group” categories together, but since you can’t create a group independently of a subscriber, then it all becomes very difficult…