You're right that people aren't having a beer with him, but that aside, charisma is one of the many things people want in a leader. It's not a necessity, and not at the top of my list, but it is a good thing for a leader to have - when dealing with foreign nations it is best if the leader is likeable, because the reaction to the leader will be more positive.
How can one expect to lead a free people if they won't freely follow him? The majority of people need someone they feel they can get behind - and they don't want to get behind a robot, it takes more than knowledge and facts to lead people.
That being said I don't think Bush is brimming with charisma, Clinton had a lot more, but he has more than Kerry - at least with the U.S. population. Badnarik has good charisma in my opinion, but since few people ever hear him speak it doesn't do him much good.
