I'd say there's a portion of non-shareholders who believe companies they like should be fighting to maximize market share, but I agree with you in-so-far as I t

I'd say there's a portion of non-shareholders who believe companies they like should be fighting to maximize market share, but I agree with you in-so-far as I think we can ignore that group for purposes of this discussion. To your point: if you're the CEO of a company, and the shareholders are pushing you to capture market share, you're quite inclined to do it. Especially since capturing market share makes it more likely your company will stay profitable or become profitable, even absent shareholder wishes. Which works until/unless you reach the point where you've gotten the combination of skill and luck and circumstance that means you end up with a monopoly market share, at which point "we" (where we == the non-shareholder general public) start posting about how your company has taken over the market and the government should declare you some combination of "common carrier" or "utility" or "out of business".