It doesn’t get thrown away though. There are 10–12 year old machines still being used, or sold for parts. Even an 8 year old MacBook Pro can still make a few hundred $$$ when sold. All the others are traded in for recycling and refurbishing. A very small percentage end up binned, and that percentage is lower and lower. I used to be a computer technician and also sold a ton of PCs. Sockets change all the time and in time, old components become eye-wateringly expensive. I remember having to order DDR-1 for a customer back in the day when DDR-3 was the standard and the price was astronomical.