Again, this sounds smart until you think about it. Apples apps such iMessage use a protocol which Apple developed. Its not even secret how it works, people have reversed engineered it multiple times and are ready to use it in other apps so people can chat to iPhone users with no issue.

The only thing stopping this is Apple saying no. It wouldnt take any extra work to allow this, they just need to say yes and then everyone in the world can talk together no matter what platform or app they are using.

Its not about creating a free and open platform, its just about saying yes to letting others play with your toys.