This probably wouldn't translate well to software. But it works great if you are installing ducts. Same goes for plumbers and electricians. My sisters first husband was a union electrician. That is why I looked into getting a union gig. I hate job hunting.
In the years I did it I worked for five different companies. I didn't have to run around dropping off resumes and doing practice tests. I just got a call from the union and was told where to go to work. And I made significantly more than my non-union counterparts. Easily more than the dues I had to pay.
Unions don't sell themselves to companies in the first place.
If you try to UBER union electricians you are probably going to be in for a rude awakening.
Unfortunately, with larger unions, or those with weaker consciousness and mis-perceptions of what a union is supposed to be - there's alienation between the member worker on one hand and the union and its operatives on the other, and then dues payment seems to be something transactional: "What will you get me in exchange for what I pay you?"
Put it this way, when I worked at startups that owed me a raise they couldn't afford, I've offered several times to take a 0% raise in exchange for a 10% reduction in hours. Not a single company has taken that offer and several thought I was trying to be funny.
I was not.