The different versions of SSH and TLS came about because the protocols' semantics needed to be revised in non-backwards compatible ways to resolve security issu

The different versions of SSH and TLS came about because the protocols' semantics needed to be revised in non-backwards compatible ways to resolve security issues. This has nothing to do with the format of the protocol. I would remind you that HTTP has also had similar revisions (0.9, 1.0, 1.1). Hyperbole about "orders of magnitude" aside, I'm not sure having a very large number of implementations should be seen as a plus. Protocols like SSH, DNS, and DHCP have relatively few implementations because the vast majority of use cases are covered perfectly well by a handful of existing libraries and tools. By comparison HTTP implementations tend to be ad-hoc and tightly coupled.