To elaborate, there are many reasons 1. They have a no ads policy which is a really godsend thing when other messengers had stickers, games and just plain annoy

To elaborate, there are many reasons 1. They have a no ads policy which is a really godsend thing when other messengers had stickers, games and just plain annoying ads. 2. The ones that did not, for ex Google etc were not really made for phones. They understood the importance of using your contacts as social graph really really well. 3. They almost never experienced outages. 4. Had sensible defaults. 5. Their apps are lightweight (memory and cpu wise) compared to amount of time one spends on it. 6. Had no api and generally very low spam compared to sms. SMS has really high spam in the developing world. 7. Rich media compared to SMS and no character restrictions I think west really hates it as most of the people there have iphone and they had this $1 signup which made it unpopular there. They never had that on android which made it a darling of non-west