You do know that on sports (say football) they play TONS of quallys so they can sort teams out after that, right? (Don't they start playing them 1/2 years before the actual event?)
And that everything they do is based on profit, right? If making a loser bracket would give them money they would do it, apparently it doesn't. We're talking about videogames here where playing a few more matches doesn't mean investing huge amounts of money.
You never played any competitive videogame, right? Cause all I play/follow always got a loser bracket on major tournaments (FGs@EVO, DotA, etc).