[asfasfo]

The UK rolled probably rolled out free SMS texts later than the US; the US was one of the first markets that rolled it out. I don't know when whatsapp rolled out there but I'm guessing it pre dates unlimited SMS being ubiquitious.

iMessage has pretty much the same feature set as Whatsapp so US users don't really have a reason to migrate at this point.

[ck425]

We had free texts before iPhones nevermind WhatsApp. Not unlimited but hundreds of SMSs a month was common. That said another thread here implied that carriers included MMS messages in free texts, not just SMS? If so that might explain as MMS aren't free in my experience.