I don't get the need for a subject line. You're always going to read a message from friends. They can screen the first line of the first message if they want. I

I don't get the need for a subject line. You're always going to read a message from friends. They can screen the first line of the first message if they want. If I want to start up a new conversation with a friend group, it should just tack onto the last conversation with that friend group.