Because landscapes are easy. The subject isn't moving, you aren't in a hurry and the phone has all the time in the world to gather enough data for a photo. Same goes for posed portraits, the phone has time to use it's processing power to make the image look amazing.

Now try to do sports photography with a mobile phone.

The first problem is lack of zoom compared to a 200mm lens. The second issue is trying to get the 1/8000 exposure you need on a rainy football field you need to stop the action for a good photo.