"Part of the beauty of an Introvert/Extrovert team is having someone you know will handle the things that drain you."
They say that opposites attract and you will find often that in a business partnership you might have one of each. The Apple Steve's come to mind. You have one guy who is the face of the company and the other guy who does a lot of work behind the scenes. The Apple Steve's needed each other and together, see what they developed.
You will also see one of each a lot in relationships. One person is quiet and the other person is a bit more out there. Maybe in a couple, one person is ready to go home while the other person is just warming up. Unless they realise that about each other, this can cause all sorts of problems.
I suppose in relationships we see things in the other person that we admire and we would like to have it in ourselves.