This is a rather bad analogy. Anyone (loosely defined) can build a bridge but it takes an engineer to design one. Legal analysis is not like the application of natural laws such as physics that engineers engage in. Lawyers write laws and other lawyers "interpret" them. Drawing and understanding force diagrams is something every first year engineering student learns. They also learn that these are not open to subjective analysis to discern their meaning. Laws are open to a certain amount of interpretation, at least that is what my lawyer friends tell me. Note that I am not saying I believe all the lawyers should be killed.
Ask yourself what other profession so openly appears to lie to the public every time they appear. In most peoples mind a trial has a good guy and a bad guy. Someone killed, cheated, whatever, someone else. It is the lawyers job to either lie to everyone and say their client didn't do it or that because of some legal loophole (written by another lawyer) the guilty should go unpunished. It's would be difficult for any profession to look good in the face of that kind of public perception. The fact is lawyers do write most of the laws and are in a better position to encode into law guarantees of an income stream than any other guild I know of. All guilds try to protect their source of revenue, most of the others have less direct access to the laws that define them.
We live in a very complex world and lawyers are a necessity. I would never argue otherwise. Anyone who argues that lawyers don't attempt to increase their necessity (and therefore their power) by making things more complex doesn't live in the real world any more than someone who advocates their abolition.
John Thornton