If the tech sector were to unionize, could that union be used to effectively push back and prevent any layoffs or acts of "doing more with less" via an aggressive PIP culture?
Unions would likely prevent this behavior (hire 10 then layoff 2) because companies with unions are much slower to hire. Instead of hiring 10 when things were going well and they were optimistic, they might hire only 1 or 2. So you'd have less layoffs, but also less people employed.
Also, unions can prevent layoffs in the short-term, but keeping the deadweight employees harms the company and the increased employment costs can make it so that a company doesn't survive a lean period and instead goes bankrupt, making everyone lose their job.