On top of that, the percentage of millionaires on HN is probably closer to 80% than 8% so that hackneyed slogan has little resonance with this audience. Then add in that many, many developers get a massive chunk of their compensation in stock or options, which literally aligns their interests with the owners of the company because they _are_ part-owners of the company, and that slogan is DOA.
Is it a feeling of imminent wealth? Or is it a feeling of equal opportunity for everyone? It seems disingenuous to frame it as "those silly Americans thinking they're about to be rich". You might as well frame unions as "protecting the most useless employees from being fired".
You're right - unions don't do that. They could be incorrectly perceived as doing that though, which is the comparison I'm making to "Americans love feeling like they're about to be rich". That's very clearly not how Americans feel and framing it that way is pure propaganda, as you put it.
You might want to look into the practices of police unions. The inability to fire for bad behavior is part of why police forces turn into self serving monstrosities.
I'm sure its a complex mix of 200+ years of socioeconomic development that goes well beyond my glib comment. I do really believe there is something to it though and understanding American culture (and politics).