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.
My grandpa didn’t mind the bites. He would chill in the garden with 5 or more of the fuckers on him and let them have at it, conciously.