Over the years I've noticed that while almost every game ends up with a "party leader" PC that it is not always a conscious decision. Old school groups, and some others, will tend to elect someone to act as a party leader. Either this is because the character has seniority in the group, makes sound decisions, or has some collection of qualities that makes them a good leader (i.e. a good charisma to talk to people, and a good con to not be too squishy if ambushed.)
Other groups will deny and fight the idea of having a party leader, all the while the very nature of human social interaction will often result in one PC being the person making the majority of the decisions, or making decisions that everyone then follows, even if there was no cognitive choice being made.
A few groups will just work without a real leader and the players discussing/voting on things. This seems to be how Critical Role works for example, though at the same time if you watch the current season you may note that Fjord tends to have more say than most in which way the group goes. Likely due to the fact everyone seems to like him IC - not that they dislike any particular members - and his high charisma.
How is it for your groups? Do you like the idea of having a set leader? Do you like being the leader? Or do you prefer a more democratic approach?