In the English Nintendo Direct on November 6th, 2019, Super Smash Bros. creator Sakurai Masahiro announced that Shiranui Mai would not appear in Super Smash Bros. Ultimate because Smash is "for good boys and girls":
"By the way, you may have noticed that a very important character from the Fatal Fury series was not included. Yes, Mai Shiranui. Super Smash Bros. Ultimate is for good boys and girls of many different ages, so we decided not to feature her. Please forgive us."
The original Japanese version of the same Direct has Sakurai use similar wording, but also explicitly calls out CERO as the reason for her omission.
The internet quickly reacted to this announcement with a flurry of memes.