PhonoPhilo: you might say that you'd be willing to join under those circumstances, but when membership is voluntary you'd actually be better off NOT joining and letting others pay for that lobbying and advocacy work. That way, you save the membership fees. THAT'S why the lobbying you want will never be done effectively: the benefits of the lobbying work accrue to both members AND non-members, yet only the members PAY for it.
Even in Canada where we have a more comprehensive licensure program than you do in the US, the licensing bodies are prevented from doing effective lobbying on behalf of their licensees- and membership in the advocacy bodies who CAN do this lobbying is voluntary. The advocacy bodies therefore have limited membership and can't afford to do anything.
For some reason, the doctors and to a lesser extent the lawyers don't suffer from this problem. Perhaps it's because unlike engineering, both of these are "true" professions- practicing without a license in either case lands you not only with a fine, but in jail- with a very good likelihood of being caught.