PTP seems to have become a bit of a misnomer in recent years with client/server seemingly being where all the money is. PTP is where it all started and will end as it’s the only scalable topology that does not cost millions to implement providing that the bandwidth between machines is adequate. TCPIP.SYS as supplied in XPSP2 deliberately (in my view) is an attempt to slow down these types of connections.
I will agree however that the delivery of viruses and Trojans via these types of connections is a major problem as they circumvent most methods of checking instead relying on the individual user to have these in place.
The Internet itself is by definition a peer-to-peer device and not reliant on any central server or groups of servers. The control of the high level protocols to me is by definition an attack on all users of the internet who connect in this way and an attempt at not to solve the problem but to centralise the solution by treating the symptoms and not the cause.