It all comes down to what your friends use. I suppose in a country like South Africa, or Poland for that matter you're very much right. Most people have Android phones, so iMessage isn't particularly helpful. This was the case for me for a long time. Eventually most of my friends and my entire family migrated to iPhones and we started using iMessages a little bit. It has some advantages over the competition - it's very well integrated with both iOS and Mac OS, while WhatsApp's desktop/web app is a bit frustrating to use, and the occasional iMessage app can come in helpful, for example Spotify. If I share a track using the iMessage app, I get an option to play the track right there in the conversation as well as add it to my library if I like it.
Also, with iOS 12.2 which is coming soon Apple made voice messages in iMessage far more useful by improving their quality which is now better than WhatsApp, but they're integrated into the system really well. If someone sends you a voice message, you can just put the phone up to your ear to listen to it, and this works literarly everywhere. The phone is locked and you see the notification on the lock screen? Raise the phone and you'll hear the message. You're working inside another app and get a banner, just lift the phone up and the message will play. You finish listening and want to reply? Same thing. Lift the phone up, talk, and when you put it away the recording will stop. It makes the voice messages incredibly convenient, and now that the quality isn't garbage anymore we'll probably end up using this a lot.
<Insert passage from "The Book Of Chrome" here>