Companies are controlled by the market, it's governments we need to worry about and find ways to control and regulate.
Companies are remarkably good at finding ways to control the market. That's why antitrust legislation is needed to protect consumers.
Every government intervention in the market will benefit established players and will hinder startups and thus the markets's self-regulating mechanisms.
There are many other cases where I'd be very uncomfortable trusting these so-called "self-regulatinf mechanisms", e.g. the abolition of slavery, child labour, and racial/sexual employment discrimination.