Public sector unions help protect public employees from the very strong tendency towards abuse and corruption inherent in political control of large numbers of

Public sector unions help protect public employees from the very strong tendency towards abuse and corruption inherent in political control of large numbers of people's salaries. They provide a counterweight to the bargaining power of government/management in sectors where it's not reasonable to expect people to change careers, and they are a subset of collective bargaining in general, which I believe is one of the cornerstones of a properly functioning labor market.