looking around a bit, it's used as an example in the documentation:

https://github.com/haiku/haiku/blob/7d07c4bc739dbf90159a5c02...

This is actually a great reason to keep it around; it's as simple as possible, and nothing uses it so it's easy to find the relevant bits of code.

Makes sense:

is_computer_on() int32 is_computer_on(); Returns 1 if the computer is on. If the computer isn't on, the value returned by this function is undefined.