How many times you took photos with your phone and for some reason the photos just didn’t come out as you expected?
Most of the times, it happens because your phone camera lens is just not clean enough. It sits in your pockets, being transferred from hand to hand, placed on tables and much more. There is a slight chance that the lens has a smudge or two.
Clean, clean clean clean. Always clean your lens before you take pictures. Just like you clean a lens on a professional camera (but easier and faster).