Despite the downvotes, this is at least partially correct. If unions were ubiquitous in the tech sector, companies would have been a lot more stingy with the hiring during ZIRP or boom eras. Or they would have been more creative with the hiring form - contractors, temporary staff, etc. None of these companies would risk locking in so many employees knowing that they'll be very expensive or impossible to fire.

I don't know about how a union would affect the standard salary being offered. I'd say that it could be higher for those essential enough to be "core staff", those that the company hires permanently knowing they'll be hard to get rid of and who drive the company forward because they're motivated with additional means.

So a union might drive the salaries and employment conditions up for the "core" team, while driving them down for the "temps". I've been through this as a unionized tech worker in both categories, and this is how it played out.