At the inception of TCP/IP, X.25 networks were already widely used, especially outside the United States. The major change, and one that would continue to be an issue for the next several years, is ...
Well, if you consider the application layer as part of the suite, then I supposed it IS part of the TCP/IP suite. You certainly don't see HTTP implemented over IPX - or at least I haven't.
Terms can sometimes play tricks on the mind. Take EtherNet/IP, for example. Many people will read “IP” as internet protocol and think that EtherNet/IP refers to plain old, standard industrial Ethernet ...