Or is it that the victims pest warning system is currently winning the biological arms race, in which case how are mosquitoes able to successfully reproduce? Or is it that mosquitoes have evolved such that their spawning numbers offset the difficulty they have biting?
Biology is hard.
The itch doesn’t begin until well after the female mosquito gets her food and leaves, so what reproductive advantage does it give to that specific mosquito over the others to make the itch not happen at all? The answer is “none”.