I think this comment misses what we're saying here in that there are many people working on things like operating systems, specialist desktop software and libra

I think this comment misses what we're saying here in that there are many people working on things like operating systems, specialist desktop software and libraries, for whom API design has nothing to do with any form of network transport at all. In my case, the company I worked at shipped a product that came with a set of header files and dynamically linked libraries that exposed some of the core functionality to the customers for use in their own software, and designing this API was a specific task in itself.