Musclehead has a theory to explain why the public dislikes lawyers:
I would argue that our problem is with our priorities. We place far too much emphasis on the primacy of clients to the detriment of our obligation to our profession, our society and ourselves. No other profession requires such allegiance to a client--doctors can refuse to perform a procedure they feel unnecessary to the patient, accountants can end their work for a client they believe is bending the rules of GAAP, teachers can teach evolution even if a parent demands creationism, etc.
The legal profession has taken the notion of zealous representation to mean whatever the client wants. The big corporate client wants to bury mom and pop in discovery? Sure... we can do that. The medical practice wants to use experts from all four corners of the US in order to make deposing them costly and time consuming for the plaintiff? No problem. All we care about is winning. There is very little consideration of the costs.
It's not a bad analysis. On the other hand, practicing lawyers can put on the brakes without violating their duty of zealous representation to their clients. To use Musclehead's analogies, I don't have to perform legal procedures that are unnecessary, even if the client wants them; and I can withdraw from a case (usually) if the client wants me to bend the rules.
If you ask me, over-the-top advertising has done far more harm to the public image of lawyers than the duty of zealous representation, especially in recent years.