How is it better for OU if every team in the conference loses?
The Selection Committe is not made up of robots... they are human and subject to human subjectiveness.
If the Big 12 constantly lost all of its first-round games (as you are stating above) it would be BAD for every team in the conference. Bad in terms of bubble teams making the tournament and bad in terms of seeding the better teams.
Example: you watch -- this year both the Big 12 and Big East will get 7 teams in the Tournament... I'll bet a large sum of money that, on the whole, the Big East teams will get better seeds. Why? Because it is perceived as a more powerful conference, no matter what the numbers say.
The more the Big 12 is perceived as a powerful basketball conference, the better it will be for all of the programs. And how do you make that perception real? By consistently winning in March.