Because there is a difference between the player (outside of the story) and the player character (inside the story) that you in places seem to overlook.
So from a story perspective, I'd look at how the companions treat you and it's not as this all powerful leader. While you as the player often have the final say, many of the important moments are framed as group decisions. For example when Gale reveals his condition, he talks to the whole group and even though you say yes or no, it is framed as a group decision and he thanks everyone when allowed to stay. Same with Wyll and Karlach, that conflict is mostly between them, even though you make the decision in the end.
Astarion and Shadowheart even make fun of your leadership role a bit. That's not what you do to your revered leader, it's what you do to your buddy who's maybe a bit too full of himself - which is probably why everyone doubles down on this if you play as Gale.
