I have to admit, Slack and Discord are much nicer to use than IRC - even something like IRCCloud (and I'm a relatively happy paying customer of IRCCloud).
It's probably due to location. LINE is absolutely dominant in Japan, Taiwan, Thailand and a few other Asian markets. None of my friends in America use it really. Facebook messenger is clearly watching LINE closely though.
Everyone likes to keep coming up with new names for the word "emote".