No one's claiming that Cain wouldn't put himself in a position to deserve another shot. The issue if he lost once again to Junior that the UFC would likely loose interest in having a competitor in a weight class that is beating other potential contendors, ala Rich Franklin and more recently Chael Sonnen.
Yeah but unlike those guys, Cain is pretty much stuck where he is. Also the age factor is a major difference there. Both Chael and Rich's best days are behind them. Cain's best days are still ahead of him and he is still pretty early in his career. He may not be a massive HW but he won't be making the 205 limit anytime soon. Not without a major overhaul. He could end up being a Fitch or Kos type except for actually being Champion at one point. He will be there for big fights and I see him being the new Mir of the division if he loses. The guy that will get the call for any Interim title fight or injury replacement.