'Pretty much' is not everyone. Adding another dimension to the information available is not a bad thing.Pretty much everyone in the world uses the ILO definition of actively looking for work.
That information belongs to other pictures. Nothing else is being eliminated, only more information is being added.Sure, but you don't need to change the definition of unemployment to see that. And by expanding it to all not working, you cannot tell who will or will not be working. You can't tell who wants to work, who is available, or what anyone is doing about working.
That information is also important and forms another part of the entire picture.They are. And they are studied. Expanding the definition of unemployed would actually hurt researching those issues. As it is, we can look at who is working, who is looking for work, who might start looking for work, who doesn't want to work etc. That would be a lot harder to do if you simply grouped everyone together as "unemployed."