to go a little deeper, corporate charters set out the values and goals of the company, as amended by the board from time to time, so it's whatever the (amended)

to go a little deeper, corporate charters set out the values and goals of the company, as amended by the board from time to time, so it's whatever the (amended) charter says (it doesn't have to be solely profit-seeking). executives are judged by their ability to deliver on the goals of the charter. baords are largely controlled by the various (professional) shareholders, and most, if not all, of them explicity seek profits above all else. that's one way markets get dominated by profit-seeking companies. the other common argument is that in capital-oriented markets, not-primarily-profit-seeking corporations are at a competitive disadvantage over time, as the extra profits of greedy corporations can push them faster/further along the technology adoption/innovation curve (or economies of scale/scope). so it's hard for such companies to survive. i don't think in practice that this is a dominant factor in competitive markets, but it's an argument often made (in business schools, for example).