The problem is that the anti–union sentiment of the Facebook employees leaks into the tools they build. Facebook may give six–figure salaries, but Facebook Workplace is used by e.g. Walmart, which has a median salary of $19,177 [0] and a notoriously bad track record of labor violations.
Why tech workers should unionize is to have a say in their company's values and deeds. [1] And when a company has an enormous influence on our country, its employees should (and do) want to be part of decisions.
It's okay, society can handle more than one issue at a time.