Contract with the unions could force the companies to not do so. The employees of tech companies have a lot of power that they’re not using right now.
Everyone knows about business cycles. It's worth saving for the unexpected layoffs so that you can make it through. To reiterate, knowing I could not have a job tomorrow every single day is not enough justification for giving up my ability to self represent. Plus, I don't have to pay people for the privlidge of losing my independence.
I think this reasoning is pretty labored. Sure there's some small percentage of engineers who are eminently employable and don't care to unionize. It benefits everyone else though, and even those "elite" engineers benefit from unionization, as unions have to represent everyone. I feel like there are tinges of, "I don't want to pay union dues if I'm not in the union" or "everyone thinks they'll be rich someday / are an elite engineer so they don't want to tax the wealthy / unionize", but idk, these are old, bad arguments.
A handful of rogue leakers or vigilante whistleblowers, backed by some non-profit defense legal fund (perhaps funded by payroll deductions, like dues), could have an outsized impact on the future of security/privacy.