The only reason for scanning stamps that I own would be if I wanted to
sell them. Stamp images in a printed or online catalog, though, are
sometimes very helpful when trying to determine what the catalog number
is for a stamp I own.

If you're a specialst in a stamp or group, then you'd need to scan for
plate ID and/or sheet position. All the early Us can be so identified
and it's a major area in the Line Engraved of GB.

With a scan record you don't have to mark the back of the stamp as
much. With software you can embed the description into the image
encoding [not visible - but as EXIF data]