There's an information imbalance. Free markets only function correct with complete information. You as an employer have access to data on market trends that I a

There's an information imbalance. Free markets only function correct with complete information. You as an employer have access to data on market trends that I as an employee do not. One function of unions is to remove that imbalance, either by removing the ability to negotiate entirely, or by providing employees with more complete information. This leads to a more efficient labor market. Presumably an efficient allocation of labor is what you want, right?