Younger bottom, younger tops

Question, how come in younger top stories, the younger partner can be shown being assertive, dominant, high labido, not vulnerable etc. but younger bottoms aren't thought of to have the same potential, people worry about their vulnerability? I just want to see younger bottoms being thought of on the same level as younger tops, where they can be assertive and dominant, and not vulnerable, and if they are vulnerable why not do the same for younger tops, portray them being vulnerable too? Idk thoughts?