I think, no one claims that. Concerning photos, your suggestion wouldn’t work for me, because I actually do not use ST for backing up the photos but for incremental synchronization. Photos are not being taken just to be backed up, right? I do it this way:
Photos from the phones are incrementally synchronized (using ST) to NAS for a Photo Album app that we use for viewing the photos (Synology Photo Station). A regular backup program (Synology Hyperbackup) backs up the photos with versioning from the Photo Station to somewhere else (to a backup disk).
Moreover, most backup programs do not have infinite history. If I followed your suggestion, how would I access the old already deleted photos?