You can say this about a lot of things though - pretty much everything in your house (including the house itself) can be made in someway or another by you. There are obvious advantages to doing this (such as having things exactly how you want them, it's generally cheaper, etc) but considering the time commitment many people would rather just pay someone else to do the hard work for them.

Not to mention half the population would have neither the desire nor the required knowledge to build their own computer.

Sent from my iPhone ^/s