I removed the READ / WRITE permissions from almost all of my apps because they are not needed there, but have still been added to the Manifest.
My motivation for this:
I would like that no (dangerous) permission at install-time has to be requested and granted for devices with Android < 6 (API level < 23).
Note: If these permissions are not removed from the Manifest, they must be granted on devices with Android versions < 6 at install-time in order to be able to install the app.