Ask HN: Is Whatsapp the new SMS?

I know there are other IM apps out there but everyone I want/need to be in touch with uses Whatsapp (well, my Mom sends an SMS every now and then). I imagine that it would have been very difficult to sell a phone back in the 90s and 00s if it didn't send/receive SMS, I also imagine that is why the SMS 'app' is part of the phone's OS and the SMS server/network belong to the carrier. Why then, have the OS/phone makers and the carriers let the new SMS be owned and controlled by one company? This is no small thing, I bought the ZTE Open with FFOS to play around with HTML5 apps but will never use it as my main phone b/c it does not run Whatsapp! Now what?