Icons are symbols; they are abstract representations. A "sunflower" doesn't tell you it's photos either, right? Did the old Safari icon tell you anything about the app, other than your familiarity with it?
Exactly. The first time you use an app you might look for the visual connection but after that you touch what you know will open it. It's not like there's visual confusion every time you want to open Photos because the icon doesn't include a photo.
Besides it says what it is right below the icon.