Earlier quoted context omitted.
A union works by artificially constraining the labor pool, reducing the employer to buying from (typically) one seller (the union) instead of many (each employee individually). Closed-shop unions, you say? Do they still exist? I work in the UK, and I've worked in many workplaces where there were active unions, and the very idea that you'd have to be a member of the union to work there was laughable and, if I recall c…
Closed-shop unions are typical where I live. My mistake on them being typical across the world. However, even in an open shop, the collective bargaining is still limiting the employer to a single vendor with respect to those it wants to hire that are engaged with the union. The only other supply is those who want to bargain on their own, and even then you're probably not going to find too many who are willing to seve…
Even that is another interesting thing; the idea that one of my employers, past and present, might actively seek out union members to employ, is so strange to me (and completely unworkable; I think it might even be illegal). The supply was in no way affected by the union.
In jobs I've had in the past, any benefits or agreement the union negotiates applied to all employees, regardless of union membership status, and were placed into contracts without any reference to unions at all. Collective bargaining by the union for improved conditions and pay existed; every employee benefited, union and non-union alike.
I suppose the moral of this is just that unions work very differently where you live to where I live.