The creation and transacting of corporate shares is also highly regulated. But it doesn’t address the question of why a third party should get a vote that helps decide a particular corporate action. Votes that limit the possible actions of all corporations equally are a different thing.

Ultimately, the corporation is operating (and gets legal support like corporate personhood and limited liability) because the public permits it through the state approving its corporate charter. The public allows the company to exist, and in exchange, the company is supposed to serve at least some vague public good. Technically, the public has the power to revoke the company's charter if that's in people's best interest.

The general public are all stakeholders that are affected by the actions of the corporations they allow to exist. They ought to have a say. In practice, we as a people have pretty much given up that say, and the world as it exists today is the result: Corporations running amok doing whatever they want, answering only to shareholders.

OP was talking about the overall social arrangement. One possibility would be to give employees (of all corporations!) some collective power over the company, as a fundamental requirement of incorporation.