This question is a bit of a cross-platform one in the sense that it's probably best answered by people with extensive knowledge of both Windows and Unix-like OSes.
I run a mixed environment (Windows, Linux, and BSD.) I'm used to the Windows ecosystem paradigm of device backup, in which the entire device (except for BIOS) can be snapshotted online, backed up to an image from that snapshot, and then restored from that image in the future. Many such systems support file(system) recovery from the image too, so that the user can recover individual files from the image without restoring the entire image itself.
However (except for Veeam) the Unix-like backup systems I've encountered do filesystem backups instead and don't support online snapshot-based imaging (Snapper claims to, but it works out of the box only with thin-provisioned LVM and Btrfs.) I'm curious because I'm trying to decide whether I should keep looking for an online imaging solution or just learn how to deal with the filesystem backup paradigm.
Why is the status quo the case?