In certain places like India, WhatsApp is the default means of communication for everyone.
You can use it without phone data if you are on wifi, it supports better quality than sms for sending images, you can video chat with it, it's cross platform, etc etc.
What's more amazing to me is that it's not more popular in western countries.
I know it's dominant, but it just sucks. To go back to the previous analogy, Whatsapp should have a monopoly on communication as much as BMW should have a monopoly on transportation.