Many years ago (80s) in the UK I remember my family and others had milk tokens to get formula milk or whatever. Each local convenience store used to exchange them for booze or cigs, at a high conversion rate obviously.
Good point about multicast - BT use it in the UK on their fibre/ADSL network to deliver live TV to their set-top boxes. I have never understood why it's not supported cross-ISP.
I believe it's very hard to implement across networks in a way that does not require core routers to become quite stateful and/or risks flooding parts of the network with multicast data nobody asked for.
There was a short conceptual revival of the multicast idea as an overlay network on top of unicast IP, under the banner of "content-addressable networks", but I haven't heard anything about that in a while.
I have one, in the glinet router i've got in our motorhome. It's fantastic - UX is shit for adding a new eSim (need to take a pic of the QR code) but once it's working it's great.
No idea why it needs an adaptor though - assume it's some buggery around being not a phone.