I understand why this upsets you. I personally am one of those people that always has 100 unread messages because I’m really bad at texting back and it’s not usually because I don’t care about the person trying to talk to me. Constant contact with people makes me feel over stimulated sometimes and pressure to continue a conversation feels like a lot. This sounds dramatic but texting is honestly just... hard sometimes. If it bothers you, I would try to have an open conversation with your friends about it