Backup can be incremental. Just the changed files are updated. A lot faster (and a lot less bandwidth or media) start to finish.
The program I used to use (MSDOS days), You (the app) opened the index and you could choose just what to recover (and sometimes: where to put it).
This is not the same as pulling 'an image' (I usually do this just after configuring a new system or before doing an OS upgrade)
At work (9-track tape era
), we did daily 'incrementals',
and Weekly, Monthly, Yearly 'Fulls' which were also stored off site