That was in 2009-2010 when WhatsApp came out. By that time SMS were free and unlimited under most plans in the US but not in other places. WhatsApp, Viber, LIN

That was in 2009-2010 when WhatsApp came out. By that time SMS were free and unlimited under most plans in the US but not in other places. WhatsApp, Viber, LINE etc. caught the non-US markets rapidly as a free alternative to an expensive service. These messaging apps didn't do as well in the US, as they had an equally free built-in alternative (SMS). Later, most operators made SMS free everywhere, but it was already too late. 10 years later, we still see the same results.