Payment is far too complex and abstract to contemplate building in at layer 3 (IP) of the network stack. Even in some idealized alternate history it would have never worked, and probably still couldn't work today.
The internet is happily chugging along on routers and switches who know nothing about the global topology of the network.
When you reduce the payment problem to 'how do we get two routers to keep track of the data passed between them' it is a non-problem that even the first generation of imps could have solved).
Why? I don't care that I will need to pay 1e-10 dollars to have a packet sent 10 times. Likewise I don't care if I lose 1e-10 dollars because someone doesn't pay for their bandwidth.
Networking is just not worth lying about until you get to sums for which lawyers can get involved, at which point you have to deal with lawyers.
