Unions exist in high demand positions too - sports, entertainment etc. Can tech unions be modelled closer to those, and less on the style of jobs you mentioned?
Yes, and professional athletes don't get promoted to management at all. Some do become managers or other executives but that requires them to retire as a player and then negotiate an entirely separate contract for the management job.
"professional athletes don't get promoted to management at all"
Neither do most employees either, what does that have to do with anything? We can't organize because there's a 5% chance that we're promoted to management?
We can't organize because the people with good leadership qualities and other important organizing skills tend to get promoted to management. It's very difficult for people to spontaneously organize without a leader.
To me it seems that we can't organize because we're selfish and naive. I don't see anyone except you fretting because of our collective organization skills :)