I'm 40 and never been on either of those. Facebook came out when I was in college. If I didn't have it I don't have a good alternative to keeping track of all the friends I made at that time. I'm sure I'm not alone with that.
Their anecdote is worth a lot more. Most people under 50 that any one knows don’t use almost every thing. It likely isn’t true that no one is using it around you. I’ve had a friend say that before when I know mutual friends who use it. There’s too many different things so most things won’t be used among any ones anecdotes. For something to be used in different anecdotes is a pretty big deal.
Are you using FB and IG and have tried friends most people you know and actively check if people are around those platforms or how else would you know? I find it hard to believe much of any one who is active on the internet does not know any one who does not use FB or IG. There are a lot more people on IG than most people realize because of it being harder to find people. For a community I run, no one knew half of the other members on IG until I listed everyone out to members.
If a random person has all their friends using any of my web apps, that’s huge. In most cases anecdotes are not worth much. Not in all cases. Not all anecdotes are specifically about billion plus people. Anecdotes were never needed for this convo any way. We have Meta’s data on the usage of their apps and their revenue.