It’s not that is the only way to talk to your friends. In some countries Whatsapp is the default way to communicate with other people because of SMS prices so if you need to talk to your friends, distant relatives or complete strangers you know you can reach them using that app.
In some cases the fastest way to communicate with a company’s customer service is through Whatsapp.
Very good UI. I keep getting connection issues when trying to upvote or navigating. Not sure if it’s my instance or the app.