You may, but others don't and it leads to lots of unnecessary scanning for some usecases. There are conflicting needs, so the compromise is that the location is added, but not enabled.

???
If I invoke 'Add/Rescan' on a specific location, I think it's pretty certain that I want to 'Add/Rescan' that location

Do you mean you need to enable it in Add/Rescan Files. This is by design, as it's not always the users intend to scan the location.

If I do a 'Add/Rescan' on a folder, the folder isn't automatically selected for scanning. I have to manually select the folder before starting the scan.

George