Why?
To keep it from, by default, automatically scanning all fixed HDD?
I have one (beta) application where on every (app) open, it would scan all "HDD", including a "phantom" A: drive of mine, which was very slow to occur, & also repopulate all ("regular") fixed HDD - with no option to remove them from its interface. Those behaviors will change before the release.
In Everything, perhaps I might run into something similar, but only once, until I go in & configure Indexes to my wants.
Answers:
1. Yes, to keep it from automatically scanning all fixed HDD, in case you have a lot of large HHDs and you don't need to scan them all.
2. You will be able to configure in advance, Network Folders.
3. Letting newbies to get familiar with "indexing", let them to control, and inform them where they can change this settings.
By default, all checkboxes of fixed HDD can be checked, as it the default behavior now.
Are there downsides?
What I would like is for Everything to index EVERYTHING by default.
I know Everything doesn't do this, yet...
What needs to be done if I do index all available NTFS / ReFS volumes by default, is make it easy for the user to abort the index creation and change which volumes are indexed without causing the UI to block (become busy).
As you mentioned the ESC key should work, however, everything will only check this once for each volume, so it might not be detected early enough.
There needs to be a progress bar with a cancel icon/button in the status bar (or something similar).
I'll look into a "select volumes to index" GUI.
It would have to take into consideration that a volume could be indexed as NTFS / ReFS or a folder index (and in the future a remote index, fat32 index etc..)