The show has morphed beyond the comic of its namesake. The showrunners have been clear that their intent is to tell the story of the DC Universe through the eyes of the Team. And as the audience ages and grows, so do the characters. Keeping them as pre-teens/teenagers limits the berth of stories that you can tell with these characters.
Just look at what Marvel has been doing with Spider-Man for the last 4-5 years; keeping him in purgatory by reincarnating him as a child.
Of course, not everyone will agree, but it's something to think about.
This article is a nice mediation on the supposed merits of infantilizing the characters that we love:
https://notthepopularopinion.wordpress.com/2021/11/19/the-grey-area-spider-man-no-way-home-a-teenagers-lament/