There are also still Telex and X.25 networks around there, not to forget the whole public telephone network! But at some point, getting a native connection to

There are also still Telex and X.25 networks around there, not to forget the whole public telephone network! But at some point, getting a native connection to all of these started becoming increasingly rare, and now these are largely emulated/tunneled on top of IP. The same can happen for IPv4.