That depends on the scene.  Fast shutter (which means smaller F-stop) for motion, slow shutter and large F-stop for really dark, but non-moving, scenes, etc.  The same as with any other camera, a 1934 Voigtlander, a new Hasselblad or the camera on a phone.  The laws of physics haven't changed much due to the advent of cameras in cellphones.  (Neither have the laws of photography - a great photographer can get a better picture with the 2MP front camera than someone who knows nothing about photography using a 42MP rear camera.)
Your question is something like "At what speed does everyone drive?"  I don't do 70mph in my driveway and I don't do 10mph on the interstate.
You use the settings most appropriate for the situation that your camera app (and camera) is capable of.