My day job consists of selling cell phones, and one of our number one marketing edge for teenagers and general millennials is iMessage, even I personally prefer using iMessage and all of my closest friends have switched to iPhone's simply because of how great, simple, and effective Apple’s texting app is.
Apple was able to get rid of the “another chat app” or “another social network” feeling by grouping it in with normal text messages — that's why they are so successful.
iMessage works, always. Everyone else always drags and doesn’t work + you can work real simply with people who don’t have iMessage and have it all in one place and have it work almost identical in terms of functions and features.
Simplicity + Ease + Intuitive = Success