Um...about 99 percent of the population just trades their computers in for new ones when they want to upgrade too.
Computers are disposable commodity items now, not expensive investments you plan to keep for years. I've heard plenty of stories of people getting viruses and, instead of getting rid of the virus, they throw the computer away and buy a new one.
As sad as the story is about people throwing out computers because they couldn't rid themselves of a virus its totally true. I would be hard pressed to find at least 10% of a starbucks consumer base who even knew what an upgradeable computer really meant.