Corps operate despite inefficiency not because of efficiency. LLC protection and market control are everything.
Ditto with market control, it's not some permanent crown you achieve. Companies have to keep performing to keep their market share.
E.g., if you opened an account at a major bank, and your transactions started failing, would you keep banking there?
A lot of people who land in that situation do continue banking there since they are either tied into that bank through loans/debt, or lack the time/energy to move elsewhere.
The argument that a market leader can screw up because it "owns" the market is not correct. Where's Xerox / IBM / Intel now?