I've wondered this exact same thing. I feel like one of my computers was haunted, but I've basically concluded that other people won't go through the steps to determine a motherboard is grounded out or a video card is over heating. They will simply throw away or donate the computer.
True story: When I was the lead for the Windows 95 escalation team, one of our engineers had a customer whose computer was inexplicably unstable. After several days of trying to fix this problem, the engineer called up the customer one day and the customer said "Oh, it's fixed."
"I just have to know -- how did you fix it?"
"Well, ever since I moved into this house, I've had problems with bad spirits. Now, when I use the computer, I sprinkle a circle of salt around it and light several candles...I haven't had any problems since!"