Apple’s default apps, such as Mail or Books, cannot be rated by users – insulating Apple’s software from the risk of negative reviews or low ratings.
Specifically, Apple designed the iOS App Store so that users are not allowed to submit a rating (like a two-star or three-star review) for certain Apple apps.
Thus, Apple immunizes itself from a form of competition its competitors must all face – effectively making Apple the only developer whose apps are listed (usually as the first result) without any negative feedback or comments.
Apple chose to eliminate ratings for its own apps to protect their placement in the App Store. According to The Wall Street Journal, Apple intentionally made App Store design decisions that benefit its own apps over competitors’:
“Apple app, Podcasts, previously averaged a 1.7-star rating before reviews were eliminated, according to Sensor Tower. It appears No. 1 in a search for podcasts.”
The Wall Street Journal, July 2019
Apple also avoided steps that would improve app quality in the App Store at the expense of its own offerings. For example:
“Phillip Shoemaker, who led the App Store review process until 2016, said Apple executives were aware of Podcasts’ poor ratings. Around 2015, his team proposed to senior executives that it purge all apps rated lower than two stars to ensure overall quality. ‘That would kill our Podcasts app,’ an Apple executive said, according to Mr. Shoemaker.”
The Wall Street Journal, July 2019