I'm not a lawyer, just a lousy unemployed paralegal. but the only advantage I can see here is that the guys who do lots of traffic tickets seem to know all the judges and have relationships with them so they can get deals that you can't get by representing yourself, so you are paying these guys because of who they know. Yeah, I know. The system sucks.
One of the Corporate Lawyers I worked for really got nailed in traffic court last year so just being a member of the bar won't always help you out. Another lawyer I know got off of a 90 mph+ ticket by exploiting a loophole and requesting documents that the officer couldn't produce in court. I have the funny feeling that officer is going to be looking for her car and next time he may have all his paperwork in order. She used to burn rubber every day going out of the parking lot.