Finding attachments.
MY guess is because all of the old machines are gone at this point. Keep in mind that units like what you are looking for were way back before the internet, before Ebay, Facebook Market Place and here. When the vacuum died it was discarded and a new one was purchased. Also these vacuums are from a time where you could most of the time go out and get them serviced and fixed at the local vacuum shop and they were also made to last. The disposable vacuum concept didn't exist back then. I look at it from this stand point as well. Dyson, Shark and brands of such that are todays market are a lot more complex with chips, boards and electrical that would be found in the space shuttle. I know this is not the reality. But I'm making a point. There is so much that can go wrong. Back in the days of GE it was plug the vacuum in turn it on and get to work. So when those vacuums finally broke it was time to upgrade and they just got thrown out. I don't really think that parts would be available now so that was all you could do was just get rid of them and move on with whatever is available in the store at that time.
That's why Ebay and Marketplace are great. I am seeing things on Market Place that are like wow. That's Great. Even Craigslist once in a while will blow your mind.