I'm guessing that what most teenagers would do is try to create an image/text in the style of a character that they already know from movies, comics, books, etc. So why not include something like that ?
I assume that copyright would be an issue. Also, I'm pretty sure Adobe wants to create the professional AI tool, so they are probably concerned with making sure everything stays on an adult level.
I also think that if kids want to use this for fun, there's plenty of opportunity....
Firefly is intended to only generate images of characters and public figures that are available for commercial use on the Stock website (excluding editorial content). It should not generate characters or public figures that are not available in the Stock data