The sarcastic tone of your response is annoying, given that it misses the point.

Yes, I do, and I use them. But when I'm amongst a group of, say, 9 other iPhone users, who happily all already use iMessage (and already have existing chats among different subgroups of the members), telling everyone they need to switch over to a different, unfamiliar messaging app doesn't go over very well. It's difficult enough to attempt this among adults; it's not surprising that teenagers would laugh in the face of another kid who attempted a "Hey guys, let's all use Signal!!" request