This is a big reason for me. Also because if anything breaks - even if my system becomes unbootable - I can select the previous generation from the boot menu, and everything is back to working.
It's very empowering, the combination of knowing that I won't irrevocably break things, and that I won't build up cruft from old packages and hand-edited config files. It's given me confidence to tinker more than I did in other distros.