Many shareholders aren't in the business of managing a company directly. They simply want to invest in companies that are run well. Just because they have the power doesn't mean they know how to wield it correctly, let alone want to be the person to do so.
If they are the majority shareholder, suing the company they are the majority shareholder in for some tort has about as much point as suing themselves for punching themselves in the face.
They could literally just do a board consent to pay themselves directly instead if they wanted to. Or direct their management to do it, since they can literally fire that management otherwise (minor edge cases of bylaws withstanding).
A minority shareholder potentially has a lot of reasons to do a shareholder lawsuit though, especially in a privately held company where they can’t easily sell their shares.
They might be getting drug along on all sorts of silly wasteful misadventures, for instance, and have no control or way to get out.
Wouldn’t they be better served by actually just doing their job? As far as to dissuade future malfeasance?
They already have all the control and power.