Twitter never took off in my area for some reason but lot of people I knew used Facebook messenger about 10 years ago which was a pain. I'm pretty sure the popularity of Whatsapp is thanks to Vodafone. They had contracts years ago that allowed unlimited use of Whatsapp without affecting your data usage. This lead a lot of people to believe that happens on all contracts. I still can't convince my Grandma that calling through Whatsapp uses both of our data.