It's not exactly forgotten. There's 2 wire Ethernet/PoE standard (used mostly in automotive) that can be daisy-chained. Designing for it however is non-trivial and few third party devices (again outside automotive market) support it.
The other issue is that there is at least 2 competing industrial connector standards for SPE, the main ones being from Harting[2] and Phoenix Contact[3]. I think this could be a great option for the future and ultimately lead to lower cost cabling and smaller products.
[1] https://www.single-pair-ethernet.com/en
This reminds me of a funny conversation I had in a small town stationers when looking for an item.
‘No, we don’t stock it. People keep asking, and I keep having to explain that there is no demand.’
Though this wasn’t for an obscure Ethernet variant.
This is something I might test myself. I have a couple of audio devices that will never be both "active" at the same time. In my current layout I need to run either two cables or just another switch and it just seems a waste. I wonder if I can buy daisy chained cable so I don't have to make one...