The way our bodies react to mosquito saliva motivates us to avoid being bitten. Which must have had evolutionary benefits, keeping us away from diseases.
I.e. all those people that didn’t mind them and never got itchy from mosquito bites appear to have died out. And mosquitoes really wish that wasn’t true.
Maybe the nighttime suckers are kinky bastards who deliberately hock a loogie in you before they leave.
The huck tuah mozzies