That's because TCP evolved as, essentially, abstraction of serial port. And due to various political & cultural & industrial lobbying, more flexible but comple

That's because TCP evolved as, essentially, abstraction of serial port. And due to various political & cultural & industrial lobbying, more flexible but complex on their face approaches (OSI) were rejected. TCP meant you could easily attach a serial terminal to a stream, a text protocol meant you could interact or debug a protocol by throwing together a sandwich, an undergrad, and a serial terminal (coffee too if they do a good job). You could also in theory use something like SMTP from a terminal attached over a TIP (which provided dial-in connection into ARPAnet where you told the TIP what host and what port you wanted). If you look through some of the old protocol definitions you'll note that a bunch of them actually refer to simplest mode of TELNET as base. Then in extension of arguably the same behaviour that blocked GOSIP mandate we have pretty much reduced internet to TCP, UDP, and bits of ICMP, because you can't depend on plain IP connectivity in a world of NAT and broken middleboxes.