Because (a) we've been enduring a stream of propaganda for decades now which promotes the idea that unions are for lazy people who use longevity of employment o

Because (a) we've been enduring a stream of propaganda for decades now which promotes the idea that unions are for lazy people who use longevity of employment over talent or drive to get promoted, and (b) anyone who has been part of a union in the US knows that if you have to strike against any powerful company, then you may be without a paycheck for up to a month of two, which completely eliminates the value of being in a union in the first place for most people.