I’m not sure how one could fail to understand how an employer won’t do anything they’re not compelled to do by law (As evidenced by the very existence of OSHA, for one.) which would include good faith negotiation with a union.

As long as the market is competitive and the agents involved are well-informed. Things like OSHA come in to play when the second requirement fails; if it is not possible for a consumer to make a well-informed purchase, then there should be reasonable protections in place for that consumer to make up for the deficiency.