I don't upgrade often so it's a good excuse for me to also clean the system. Otherwise, I could be less bothered to sit there and reinstall everything if I wasn't doing a hardware upgrade. MB upgrade (CPU at same time) are normally the only real reasons I do clean installs. Other devices don't warrant enough reason to do clean install unless there are driver conflicts that are unresolvable. The only exception is an SSD, whereby for it to be aligned properly, it is easier for me to allow the OS to do this during partition creation/formatting portion of installation.