Because caring directly about shareholder value is a distraction from what I'm actually there to do. If I focus on shareholders, that leaves less time and energy doing my actual job and would make it more likely that I make decisions that make our products worse. If I'm doing that, then what's the point? I may as well be an MBA or something.

There is division of responsibilities for a reason. I also don't care directly about the bookkeeping, HR, etc., for the same reason. That's not to say I don't care in the absolute. I just don't (and can't) care about those things directly. I contribute by doing good work.