That's because many people keep harping on the idea of protecting data.
Data is: Documents, Pictures, Music & video
And while data does need to be protected so does our OS installation
Which has "settings" and preferences that must be preserved.
and your programs/applications
(and those while replaceable also have settings that need to be preserved)
And While I protect my Data, programs and OS installation in the ocnventional way
(the way I've done it lets me migrate to another computer with a virgin but activated
OS in about an hour)
the only rational way to protect your OS and program files and all those pesky
settings is to clone your OS drive.