Because nobody thinks this?
The odds on Bama missing the playoffs are much longer than the odds of them losing currently.
The point is, narratives matter. And the bullshit narrative is why "nobody thinks this." So why not introduce a much more reasonable narrative?
The only reason why Palmer and Tess kept focusing on the possibility of Miami leapfrogging ND is because they now expect BYU to drop in the rankings due to their 27-point loss. Why wouldn't they take the next logical step and speculate that a double-digit Bama loss would also drop them, therefore making the conversation more about the last spot going to Miami or Bama rather than Miami or ND?
The reason why they didn't do that is the problem. It doesn't hurt their bottom line to speculate about ND being left out, but it would if they speculated about Bama.