I have no basis for this, but I think this is also based on personal genetics or similar. Most of the bites I get seem to create no bumps or itchiness at all. When i was a kid, that wasn't the same, but now in my late 30s it seems to no phase me.
And for personal anecdotal evidence, my wife gets more problems with mosquitos here than I do. When we visit her home country I get more problems than she does.