All the Hollywood & TV & Stage unions do that.
Also professional sports unions.
The Bar Associations and the AMA are not quite unions though they certainly advocate and lobby strongly on behalf of their professions.
For the Bar there may be confusion because of the names of licensing agencies. In California, the state agency is the State Bar of California, but that has nothing to do with various bar associations.
As a counter-example to this specific point, the Screen Actors Guild does a tremendous amount of work to raise the pay and conditions of the median earning actors, without preventing the highest performing members from negotiating compensation in line with their ability to contribute to the success of a project. We can have our cake (collective negotiation) and eat it too (million dollar+/yr IC roles).
Other notable examples; State bar associations (lawyers) and the American Medical Association (doctors).