[uep]

Do they though?

Everything as a file is an abstraction, an enormously useful abstraction. The point isn't that it has to behave like a file in every way. At the C level, the fact that open(), read(), write(), or e/poll() behave the similarly is extremely helpful.

I can have a whole suite of functions that do not care what type of file descriptor they hold, but just that those functions behave in a predictable way. Maybe only 10% of my code has to care about the differences between them, instead of 70%.