It wasn't always this way. The individual permissions used to be displayed to the user directly; newer releases of the Play Store have "streamlined" this permissions prompt so that users see general permissions "groups", and some permissions (such as INTERNET) are considered "not dangerous", requiring a click on the "See all permissions" button to view everything the app requests.
I imagine it's because Google recognized the general insanity of the system, and presenting fewer "scary" permissions improved conversion rates.
Then they threw the whole system out with Android 6.0, moving to a much more sane flow for everyone involved, where the user is able to grant or deny individual permissions at runtime.