I don't know why...youth doesn't hold any real power some artists are just insecure and afraid of looking old and dusty to younger audiences
Youth holds a lot of weight in the entertainment industry. It can be the difference between getting a role, endorsement, and even people buying your music. This is especially true for actors and actresses because older actors and actresses will be passed over for roles in favor of the younger, newer sensation.
Look at someone like Madonna. She looks ridiculous trying to remain youthful and even though she's an iconic artist, a new Madonna album isn't going to get the same attention that a new Olivia Rodrigo album will. Touring is where it's at for Madonna. New music? Not so much.