I think a lot of programmers see themselves as more independent, and kind of distrust things that take away said independence like unions or accreditation. So

I think a lot of programmers see themselves as more independent, and kind of distrust things that take away said independence like unions or accreditation. So they'd worry about a union bringing about things like Global Rule One (from the Screen Actors Guild) where union talent can't work in a non union environment (or vice versa). Or that joining a union would somehow become mandatory, like it is in some other industries. In other words, they like how anyone can get into programming, that you don't need a specific degree or to pass a specific test to start and that it's up to the worker to choose what company or organisation they want to work for. And they worry that if programmers were unionised, this would stop being possible somewhere down the line. That and they're decently well paid anyway. So they might think they need a union less than say, factory workers or public transport drivers.