The vast majority of them got unceremoniously dumped into landfills or run through recycler shredders after they had outlived their useful lives. The only reason most of this stuff is collectible today is because most of what was made has since been junked. I remember parting out a stack of Apple II machines back in the early 90s. They sold pallets and pallets of them for peanuts at school auctions. I was always one to salvage potentially useful bits rather than just chuck stuff though. For a while you could hardly give them away. It was like VCRs and VHS tapes are currently, today's trash is tomorrow's sought after collectible.