I agree with that. I have no idea why it’s in a separate package. But I can say that about many packages :).

It’s possible to just treat everything as a promise by wrapping results in Promise.resolve() but that can have performance implications that some franeworks might want to avoid by only going down the promise route when they have to.

For promise implementations, If the callback to then() returns a promise, the promise implementation detects that and resolves that promise behind the scenes: http://www.mattgreer.org/articles/promises-in-wicked-detail/...