Maybe because a lot of people on HN are small business owners, and unions take power away from business owners and can and will force you to do things to the detriment of your business if they deem it in the best interests of the union members.
A lot of small business owners who also happened to work for a union and had a bad experience? That seems like a lot for a site largely filled with software developers. Is HN more mainstream than I'm giving credit?
A union is a company that represents the interests of workers in the same way that a company is an entity that represents the interests of capitalists.
Besides, many people on HN work for tech companies like Adobe, Apple, Google, Intel, Intuit, Pixar, Lucasfilm or eBay, all of which were found guilty of colluding[1] to keep engineer salary below market value.
[1] https://en.wikipedia.org/wiki/High-Tech_Employee_Antitrust_L...
People tend to forget that unions represent the existing employees, not aspiring hires. This can actually work to the detriment of juniors and newcomers to the industry. It can also work to the detriment of teams where it becomes intensely difficult to fire people who are legitimately underperforming. The public school unions keeping bad teachers on the payroll but keeping them idle in empty rooms is a prime example. Police unions defending bad cops is another very relevant example. If you’re an aspiring teacher or police officer with motivation to do well, why should those union employees take a spot on the job that you could otherwise occupy and do better? Switching the rules of the game to favor seniority doesn’t benefit people who rank low on the seniority ladder.
My understanding is that the related civil class action suit recouped small fractions of estimated lost wages, though there's a lot of hand-waving there and both sides are going to wave their hands differently.
I might be mistaken; this didn't affect me too much, and I most mostly just amused how incredibly afraid of Steve Jobs everyone was.
There is no need to wait for a "tech union" to unionize tech offices. Kickstarter unionized last year under the Office and Professional Employees International Union.
Most people also think they are smarter than average. I have seen people that thought they were great at negotiating their own wages/benefits in a ritualized yearly pissing match with their boss only to be outdone by new hires. Lots of overinflated egos around that would rather rip their own arms of than pull on the same rope.