It is time.
http://www.linuxmint.com/
Maybe not. Perhaps the user likes using an operating system that has to be reloaded every year? Perhaps he feels a need to dedicate an hour or so of his computer's processing time to virus/malware scanners. Maybe he likes using an OS that you can't really restore to your previous settings without spending time re-customizing your desktop. Perhaps he thinks it is a good idea to let a program run just because the filename ends in 'exe', 'com', or 'bat'.
You never know, his time could be worth nothing, so the constant battle against malware doesn't really cost him anything.