The people downvoting this don't understand how intimidating building and upgrading PCs is to the average person. Like seriously, there's a reason prebuilts exist. Building a PC may seem easy if you're used to doing it, but most people aren't.
A lot of people see a PC as this magic box that runs games and other programs, and they don't dare open it up for fear of breaking something. Heck, a lot of people don't even understand that an operating system is just a piece of software that can be swapped out for other software, and not an integral part of the system they're using.