Nowadays we call those APIs. They are REST based rather than file-based to make them distributed, the main difference is that you don't get a common user interface that all providers adjust to; you need to choose your own client to read them and write into them.
And because they're created by programmers for programmers, they're not what you'd call user-friendly. Usually the only efficient way to use them is programmatically, so that you need to create a specific user interface for each API. Somehow, I doubt that Cairo would have come to be anything much different from that in the end.