> A careful reader may have gotten the impression that SCION is simply source routing in disguise, however, this is not the case for a variety of reasons. First of all, end hosts do not learn any information about topology inside the Autonomous System (AS) - this is still under the control of the local network administrators who may want to implement complicated firewall rules or in any other way affect the traffic in their local networks.
> While with SCION the end-host selects the path of the packet, it cannot perform this selection completely independently. Instead, the network operator distributes the available paths and the end-host can only choose from this pre-selected set.
[1] https://www.anapaya.net/blog/the-scion-series-part-1
Now that we can calculate routes trivially on consumer grade hardware, perhaps that's a forcing function?
Come to think of it, I see this as a conceptual extension and optimization on BGP Policy Based routing. Seems like it's removing the overhead and formally separating the control protocols from the data protocols.
IMHO, source routing concept is not abandoned as Segment Routing seems to be used in specialized / large networks: