They might have a conflict of interest so that they shouldn't be trusted implicitly even if they can theoretically do a better job. Also, we live in a democracy, and these are public companies. With that much money on the line, they become quasi-governmental in shaping the economy and such. If they don't like public scrutiny, probably best not to be a public company. The workings of a public company should probably be a public interest, so the public can support laws and regulations appropriate for them