Social reality and culture work a lot like improv comedy. We often don't know "who we are" or what's going on socially, but everyone unconsciously tries to establish expectations of one another. Understanding this dynamic can give you more freedom to change your role in social interactions.
This almost seems too obvious to say, but one reason to be bothered by the move from "tall" to "leader" is that sometimes you want your group to have a leader with skills that cause the group to succeed, and the most optimal choice for that might not be the tallest person.