The PC has been with us for some thirty odd years now. The way they're built and sold, it's not expected that they last very long. What's a computer's life span, anyway? One year? Two years? Three? But certainly no more than five, at least nowadays.
So what happens to your computers when you don't want them anymore? Some years back, the ready answer would have been: donate 'em to the less fortunate. That sounds great in theory, and right charitable, too. But you can only hand down a computer so many times before your giftee will refuse to take it. Not even if you pay them.
What then? Sell the computer for scrap metal seems to be the only other option. And that's just what happens.