A couple weeks back, Nintendo’s Kensuke Tanabe spoke to VGC about a design edict with Paper Mario games that was put in place since Paper Mario: Sticker Star. According to Tanabe, Paper Mario games can "no longer modify/create characters" tied to the Mario universe. While fans are still looking for an explanation as to why that is, Tanabe has been a bit more specific about the mandate.
In an interview with GamesRadar on the same subject, Tanabe had this to say.
"From the production of Paper Mario: Sticker Star onwards, we were no longer able to graphically represent individual characteristics, such as age, gender etc., in the Toad NPCs (non-playable characters), and so it has become that much more important to convey their personalities simply through text. Our writer, Mr Taro Kudo, has been grappling with this difficult challenge since Paper Mario: Sticker Star, but has managed to achieve giving all the texts a sense of humour. In this instalment, Paper Mario: The Origami King, we were able to include some Toads wearing an outfit to match their role, and also created original origami characters."
What we're really looking for from Nintendo is an explanation as to why this is. Fans know that the series used to allow for this kind of expression, and removing it seems like a rather odd decision. Even if we don't like the answer, hopefully Nintendo will explain themselves in a future interview.