It's quite popular in countries where buying SMS credits is not always an afforded cost, but public wifi is everywhere. Basic Android phones are fairly popular and inexpensive given that they double as a web browser and communication device for many.
Here in Vietnam you can get unlimited 3g access for $2/month and once you've paid for that using something like WhatsApp is much cheaper than paying the SMS fee for every message.
That's understandable, but my question was about creating WhatsApp vs making a regular conformant XMPP/Jingle client which also simply works through TCP and UDP. The later gives free choice of what XMPP server to use and allows communicating with users of other federated servers. WhatsApp allows communicating only with WhatsApp if I understand correctly.
I would imagine this is a plus for them, sadly. It's probably easier to extract revenue from a walled garden than an equally user-friendly XMPP client.
