Because they carry nasty diseases and get into cupboards and eat food which puts germs on that food which obviously carry dieseases
I think people don't like mice because it is natural instinct because yes they can carry dieseses but its usually rare, also some people think they are duisgusting and dirty but actually they are one of the cleanest animals, they groom themselves constantly like cats. Mostly because they poop. But I don't have anything against mice. Ha I love em!