That's pretty clearly not the case. Unions aren't about being 'treated well' in so many cases, they're about granting power to the union organisers.
Look at Kickstarter. They got a union because they took down a project that was violating their own terms of service by fund-raising for political violence. The union organisers primary aim was literally to force Kickstarter to support violence against conservatives. Being treated well had nothing to do with it. Look at Google. A pampered workforce, talking of unionising to try and force the organisation even further to the left.
Smart managers fight unions with everything they've got, or else the most hard-left workers they've got will take over the company by force and subvert it to evil political ends.