Why only an api for input?

Wouldn't it be reasonable to have an api for in and output?
Since many things have a combination of both and sometimes are really related.
touchscreen = screen (output) + touch (input).

I don't know this for sure but wouldn't having two seperate api's be less convenient for integration of complicated input+output devices? Maybe there can be some benefits to integrating something. And with having to change something in two specifications this could proove to be more difficult.

Thank u for reading.