I have fly swatters in several rooms in my house. If I know there's a fly inside my home, I go on the prowl like the friggin' Terminator. Flies like to hang out in dead flesh and road kill and they lay their eggs in feces (makes me urpy just thinking about it). I sure as hell don't want them landing on my food or kitchen utensils and dive bombing me while I sleep.
One day last week, I swear I killed about a dozen flies inside my home in one day! one or two is not unusual, but a dozen... that's excessive. But in the fall they don't fly as fast. It must be the cooler weather. They're pretty easy to stalk and then swat to kingdom come.