To save time obviously. If one stays home all day, he can backup, format, reinstall Windows and all of his applications and games in 2-3 days. Remember we are talking about a typical HOME PC, not an office PC with 3-4 applications. If he, like most of us, goes at work and then he has to deal with kids and live his life, he has VERY limited free time, usually late at the evening, so he needs more than a full week, maybe two weeks to do it. No thanks, I would prefer to watch a movie or series with my wife at that time and sleep at a reasonable time, not too late, so I will avoid a clean installation at all costs. I would even use magic, if possible, to resurrect a dead disk. Besides, as I have already said in my previous post, it CAN be done and all you have to do is install drivers for the new hardware and activate your apps. The newer the Windows version, the less likely it is to see a BSOD. This was back in the Windows XP and Vista days. Even Windows 7 can tolerate moderate change in hardware because most drivers are built-in.