Because nothing prevents you from representing yourself. (Unlike Massoui) presumably you have your own interests to look out for. When you represent someone else for money (a concept my clients can't seem to fathom when they get the bill) you have your interests and your clients interests involved. Being a member of a particular State's Bar means you are, at least nominally, competent to act on behalf of someone else AND you are upheld to that state's code of conduct.