Why is avenging your losses to fighters you should have beaten so highly valued?

Specifically when discussing GSP's record his fans always mention that he avenged his losses. But the fact of the matter is he should have NEVER lost to those opponents in the first place. Avenging the loss doesn't erase it.

Of course GSP was going to win the rematch against Serra, wouldn't it be better for his record if he beat say another contender like Kos, Fitch, or Shields again?

The only reason GSP was even able to avenge his losses was because of pure luck of the circumstances....

Why is avenging your losses to fighters you should have beaten so highly valued?