To use language you may grasp

Economically the market seems to benefit union members individually over non-union workers, so logically it makes more sese as an employee to join a union than it does to be non-union.
For employers unions reduce the economic benefits of business so they seem illogical - this is a conflicit of interest, it would be illogical for an employee to be non-union and recieve less pay and benfits than to be union and recieve more benfits due to collective bargining strenght.

Plus I may add that is very socialist of you to ask an individual to give up personal benefits for communal benefit.