While I see the point that you are trying to make - one could also argue that the onus is on the dude that owns (and insures) the bus, train, or airplane. If something goes wrong - THEY are the ones that will be liable...
Granted that's the "deregulate everything" model...
Who owns and insures the lawyer? Most of us are self employed and lawyers are unlikely to tell you how horrible they are...or to even know it.
Where do you go to "check out" your lawyer? What web search do you run? How do you know it's accurate? What book do you look in? With few exceptions, lawyers get named to lists of "greatness" based upon how big an ad they buy in the publication. Mar-Hub is an exception, but there, you are rated based on what lawyers and judges think of you which is not exactly objective. I'm a Martindale Hubbell AV rated lawyer, but I know unrated lawyers who are very good and fellow AV rated lawyers who I wouldn't send my dog to.
The consequences of a poor lawyer, as a poor doctor, are dire and it is difficult to verify how good the professional is. Some of the best doctors have been sued the most and have high mortality rates. Why? Because they are willing to take on the toughest cases in the worst situations.
There is a role for professional licensing and regulation.