I'm not advocating for not having unions, but the idea some people have and corporations push is based on a hypothesis that companies will try their best to minimize costs.

Unions do have these real benefits for the workers who are a part of them, and these benefits come at the cost of the corporations who have to pay more and implement better practices.

This increases the cost of human labor, so when doing a purely greedy analysis of costs vs revenue, the costs go up for processes which requires human labor, which drives down the profit, disincentivizing investment or even the continuation of processes that require unionized labor. Overall, there winds up being less demand for human labor and more demand for automation.

I'm not here to speak on the truth of this, I think of it from this perspective: Information asymmetry (not understanding the opposing argument) benefits the party who has the information, so understanding their argument is necessary if you want to counter it.