Because of course all conferences are equal and beating out Georgia, Bama, Ole Miss, aTm, Arkansas, and Mississippi State (all ranked) to win the SEC is exactly the same accomplishment as beating out Cincy and Houston to win the AAC.
Of course they're not equal. That's why the idea is a 5+1+2 or a 6+2 model.
In 2016, 2017, 2018, and 2020 a P5 non-champ was selected over P5 champs. There are arguments for why that is the case, in that it was Notre Dame (who gets undeserved treatment because of that
shiny gold helmet) twice, but for the most part it was simple "count the number of losses" accounting.
Of all those seasons, the worst P5 champ, by record, was 10-3 Washington. All three of their losses were road games (technically Auburn was neutral, but Washington traveled from Seattle to Atlanta, and Auburn traveled from... Auburn to Atlanta), and two of those were to ranked teams at the time. All three losses were one-score games, by a combined 10 points, with one being a loss in OT. The worst by ranking was 2020 Oregon at 25th (4-2 record), so if you had a 6+2 system they'd have been replaced in the playoff by #12 undefeated Coastal Carolina.
Would it be THAT bad to give every P5 champ an auto-bid?
Then you've got the G5 champ... In 4 of those years, the top G5 champ was undefeated. In two others, the top G5 champ was a 1-loss team in the top 20, and the worst (by record) was a 2-loss Boise State team ranked 20th.
Would it be THAT bad to give the top G5 champ an auto-bid?
Finally, there's an argument that you'd be leaving deserving teams out by allowing undeserving conference champs in. Well, in 7 years of the CFP, we've never had more than one team that was a P5 non-champ selected to the top 4. Now I'm giving you 2 slots for at-large. You can't make the argument at ALL that deserving teams will be left out at a higher rate than the current system.
It satisfies everyone. Conference championships are meaningful. The G5 gets one seat at the table. The "best teams" are not left out because you have two at-large spots.
But I'm just CRAZY for suggesting this, huh? Because the entire idea of a college football championship is a farce if we let Cincy in this year.