I don’t want to make assumptions, but your reply makes me think you arrived at Hangouts once it was already being deprecated by Google. Granted, being US based I didn’t need the coverage of WhatsApp (limited as they was even then to phone # accounts), the scant usage of Viber or the other innumerable messaging apps I touched in that time period. Hangouts integrated seamlessly with SMS, let me send media/stickers/map embeds to mixed-platform groups never worrying about quality downgrade. And did I mention that one could access Hangouts (and its SMS pass through server) from any machine in the world through Gmail? iMessage makes you jump hoops to do that shit today.