Why aren't Debates done in brackets?

On the news that Donald Trump's debate is off and Colbert is now planning a debate, thought I should talk about something that seems like common sense to me but seems to evade the main stream media.
Why can't we have primary debates be a series of one on one brackets?

Let's assume it's because they are incompetent not because of a conspiracy, at least for the sake of this blog.
Let's assume that the 24 hour news stations actually care about informing the public.

The best way to do that would be to have, not one debate, but a series of debates. Invite all of the candidates and randomly pair them up.  give each pair a set amount of time. Audience votes for who wins each round. Half are eliminated. The other half keep going. You could even have the losers of the first round have their own division (wild card) and the winner of each division can then debate each other.
abracadabra everyone gets equal time. None of the drama. None of the favoritism. If each round gets the same questions there isn't any softballs.

It seems extremely strange that a sports obsessed culture wouldn't use this method as the default. It seems obvious to me and I don't care for sports, at all.


PS
The graphic above I randomly wrote down ten candidates. Then I used a dice rolling ap with two ten sided dice. Used the rolls for that  to pick which two candidates would be together. Then for the eight remaining I used an eight sided and so on until all the candidates were paired up.