Oh its because you're so sweet! You know for the life of me I cant figure out why they do that. Theres a whole house here to fly around and do what ever a fly does. but no they want to be right there in your space licking your face like they are some cute puppy! Anything but cute and much dummer than a pup, at least the pup knows when I say no! You would think that it would become natural instict as with other creatures to stay away from us humans, cause we'll kill you if we get the chance.