You gain three major benefits by bringing your camera:
- Zoom (as mentioned), and generally better optics and smaller depth of field.
- Low light capability ... even a 7 year old point and shoot is better (though not by much) in low light than the newest cell phones.
- You're not killing your cell phone batteries taking photos all day.

And one smaller benefit, cameras are generally better to use (ergonomically) as cameras than your phone. So long as it's small, I'd bring it anyway.