Comment by dragonwriter

Lobbying for legislation is a tangential part of what a labor union does, and lots of organizations that aren't labor unions also do that. Labor unions first and foremost do collective bargaining on behalf of employees with the business owners who employ them. ABA and AMA don't do that.

ABA and AMA are professional associations, like ACM, that happen to have effective lobbying arms, and their members are often independent business owners rather than employees.