It's misleading to just say "because of the green text" it's so much more than that. If you have an active iMessage chat and users are using iMessage features, it's a weird experience for the non-iMessage folks.
It seemed like a real victory to have emojis in the UTF format, but of course now Apple turns on the big FU and finds other ways to chide non-iMessage users.
Don't blame the kids.