Because there are other people who could have won those fights, and the very purpose of a rating system is to assign higher numbers for the people who win and lower for those who lose.
We understand the frustration that can be caused by a losing streak, but a winning streak can cancel out the effect. You can't expect to have a losing average and continue to climb rankings forever, (as some had wrongly guessed was possible with this new system) as that is not the case.
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Computing the probability that at least one of the following events will occur:
P(a or b ... or z) = 1  P(!a and !b ... and !z)
Probability
