You can install it from the repo fairly easily. As we can not install every single application, is there any specific reason we should have it by default?

Skanlite is nice and work just fine. But it's a frontend to the Sane backend. So you have to provide a proper support to Sane, and this requires additional space. However I did it for my remix [1], as a "workstation" edition (alternative to the lighter "desktop" edition).

[1] https://github.com/mbugni/fedora-remix

You can install it from the repo fairly easily. As we can not install every single application, is there any specific reason we should have it by default?

Workstation spin has gnome-scan

A scanner app is pretty basic functionality so IMO it makes sense.

I'd prefer Skanpage, as it supports multi-page scans.

Ping.

I agree with @ngraham - Skanpage allows saving as PDF which is what I imagine most users will need if, like me, they only use their scanner to scan signed documents.

I tried both scanlite and skanpage. My preference is scanpage.

A scanner app is pretty basic functionality so IMO it makes sense.

I'd prefer Skanpage, as it supports multi-page scans.

I use the Gnome "Document scanner" because it supports directly clipping the image, which neither Skanlite nor Skanpage appear to do in any obvious way. I do this all the time.