"Leader" is a word with a number of different meanings which are influenced by context. A leader is a person with leadership abilities. Leadership, is defined as the ability of an individual, group, or organization to influence, or guide other individuals, teams, or organizations. How one becomes a leader often depends on what needs to be led.
I think we are lucky in our political system in that our Party leaders are, for the most part, chosen by the group they lead. That allows us to replace underperforming leaders during the course of a parloiamentary period, and not have to wait for General Elections as is necessary in the USA. Our Prime Ministers and Premiers are the spokespersons for the government when talking about matters in general. What I would like to see at a press conference is for the leader to introduce the topic for the press conference and then introduce the relevant Minister who would then go into the details. I see the leader in such a circumstance as being like a Master of Ceremonies who is there to introduce the acts.