The predominant "problem" with restoring from snapshot backups (or indeed, even worse, attempting to use the built-in Windows Restore functionality !) is as has been mentioned by crewmeal above .... how do you know when your last known good clean snapshot backup was ?
The secondary issue I have with them is the waste of space... you're wasting gigabytes of disk space backing up software .... that means you have to over provision your capacity.... which, if you're backing up to multiple robust devices, as you should .... equals $$$.
Don't get me wrong, configured correctly, in the right circumstances I like snapshot backups... for example I use Apple TimeMachine for example... but I have it configured to exclude Applications and System Files.
The whole point of backups is to keep safe stuff you cannot recover by other means. Software and operating systems can easily be recovered (even if its a slight pain to dig through your emails for license codes ... but because you'd have backed up your emails, that's not much of an issue either).
For most people, starting afresh with a clean install after having used a computer for a few years is going to be no bad thing.... they accumulate garbage over the years and that has a tendency to cause slow downs depending how many services are running in the background. Even more so if you're dealing with a family computer used by kids !
On the other hand, I can't complain too much... since you're actually making the effort to do regular backups ! Just don't forget to do a test restore once in a while !