It is easier to associate a charismatic personality with extroverted people. The exemplify outgoing, and “life of the party” personas. Charisma is associated with a warm heart and so the listening skills of the introvert come in handy. Johnny Carson learned to have a stage presence, but in real life he was a very quiet and personal man. I believe that his ability to let others talk, to bring out the best in others, made him the star that he was.
Since people “feel” charisma, that it is something that they sense, the humanoid who must be the life of the party may be so busy “shining” that they miss those who are the audience.