In his dissent in the Citizen United v. FEC case, Justice Stevens reveals a rather pernicious understanding of the reason society validates the corporate form:
Unlike other interest groups, business corporations have been “effectively delegated responsibility for ensuring society’s economic welfare ....
No. They haven't. It is true that a corporation must have a certificate of incorporation from the state to obtain legal recognition as such. We might reasonably infer from Stevens' comment, however, that he accepts some version of the old concession theory, pursuant to which the corporation was regarded as a quasi-state actor exercising powers delegated by the state. It has been over half-a-century since corporate legal theory, of any political or economic stripe, took the concession theory seriously. In particular, concession theory is plainly inconsistent with the contractarian model of the firm, which treats corporate law as nothing more than a set of standard form contract terms provided by the state to facilitate private ordering.
The state provides the corporate form not so the corporation can ensure social welfare, but solely as a means of facilitating private ordering amongst people.
The point goes directly to Stevens' argument that the corporation had no First Amendment rights that were infringed by the law at issue in Citizens United. When the state wrongfully interferes with how those people have ordered their relationships, those people need the protections of the Constitution. Collective action problems of various sorts may prevent them from banding together to vindicate their rights. Accordingly, the law allows the corporation--under the control of its board of directors--to seek the necessary Constitutional protections on behalf of the community of stakeholders (and, especially, the shareholders who hold the residual claim).
In contrast, the logic of Stevens' view would allow the state to hijack the corporation whenever it feels like it.