The IBM PC and particularly the later IBM PC AT (and PS/2s ) had really well designed keyboard particularly compared to many of its competitors. I believe the explanation is the IBM had a tremendous amount of experience with typewriters (the IBM Selectric typewriters with the interchangeable spherical typeball elements (”golf ball”) were dominant in business and government offices for many years, apparently justly.) IBM also had a lot of experience in keyboards in several generations of CRT displays, 2260, 327Xs, the Displaywriter, and shortly before the IBM PC 5150 was introduced, a product called the Datamaster, a small business computer which shares some design elements with the IBM PC.
The PCs keyboard wasn’t quite perfect but it was pretty good, both in layout, and in presence of PF (Program Function) keys. A feature I think they got from the 327X CRT displays. The keyboards were solid, reliable, gave a positive tactile and audio feedback hen a key was pressed, which is important for a touch typist. The IBM PC AT introduced in 1984 improved the keyboard even more. The “enhanced” version of these keyboards ere called the Model M.
The AT changed the electrical interface so that the “AT” keyboards were not compatible with the PC/PC XT keyboard (There were some keyboards with PC/AT compatibility switch I am not sure if these were made by IBM or a 3rd party). The AT keyboard was carried over nto the PS/2 family with not much change other than changing the connector to a PS/2 mini-DIN connector. There are a large number f models and variants. Sometime in the process IBM spun off its typewriter (and small scale printer) division located in Lexington Kentucky, which became a company called Lexmark. Many Model M variants were made by Lexmark over the years, eventually the keyboard business was sold to a company called Unicomp which continued to make variants of the Model M. The Model M keyboards are still sought after today by cognoscenti and people who keyboard a lot, because of their superior typing characteristics and reliability. Model M keyboards appear fairly frequently on Ebay because of this demand. I am typing this on a 20 year old Model M Part No 1391401 made Nov 24, 1987 (It’s hooked to a keyboad video mouse (KVM) switch box and I use it on 4 different computers, none of them made by IBM.) For some people the presence of a good keyboard was an important selling point for the IBM PC and successors over their competition.