I have to. But in this case it's not a social network, I don't care if the rest of world uses WhatsApp. I don't need a "network effect". I am fine when the people around me use it. So I achieved my personal goal and while I am happy if more people will join, it will not impact my own usage.
He means you have to be "that guy" that people actually listen to and would switch apps for.
Well, if no one listens to you why even make the effort to keep in touch. That's a different problem and solved by Twitter and similar
Um, I'm not being literal about "listening". I mean a person who is popular enough that if they leave a platform others will follow them.
I have to be that guy for the family chat list as well. So I already have practice.