Because people gravitate to things that are free, especially in third world countries. And not just because they can't afford it - it can be issues such as not

Because people gravitate to things that are free, especially in third world countries. And not just because they can't afford it - it can be issues such as not having a credit card. The reason whatsapp got traction in the first place was it was free (for a year+) when SMS was not. If Whatsapp cost $1 then people would use whatever was free.