Unions can also block career paths because of seniority preference, a newer guy won't be considered for promotions even if he is more than capable and has showed dedication if the older one are given preference just by longevity. I'm not against unions in general for blue collar jobs but I do believe that they shouldn't have more power than the company, it's all about balance. I come from a country where the lefty populist government used unions to destroy all the private sector by giving them all the power.