Because I was a newb at the time and I just installed the app and it took those permissions as default. I am not a slow learner though. That is what prompted me to start digging into what else this app was doing and its eventual shut down of any network communication. One of the main reasons I shut it down was I don't want DJI flipping some bit and force an upgrade or no fly situation and I am sure they can do that based on what I see in the code as there is an expiration date in your firmware, if I recall right it is one year after a particular firmware is released, though to my knowldege, they haven't enforced this yet.
Another reason is the white paper from DJI to use a comm channel for drone identification. This was probably integrated into the drone somewhere around firmware 0700 and is why your range slightly decreased, and along with it also came NFZ zones which was marking my house, which is no where near a major airport, as a restricted zone. It also started giving me false warnings about signal range when the drone was probably 50 feet from me when other firmwares did not.
Anyway, most of you think you control your drone. I will be the first to tell you that you do not and that is only an illusion. That doesn't mean you can't take back control of it however.
I understand your concerns about privacy but, frankly, you seem to be verging on paranoia - taking every little thing that you don't immediately understand and ascribing it to some kind of evil DJI scheme. At least get your facts straight before you start rampant speculation and broadcasting misinformation. I can't comment authoritatively on the app taking selfies on your Android device and sending them to DJI, but that just doesn't sound credible. As for expiration dates in the firmware, there aren't any that I've seen so far, and I have two-year old firmware running on one of my Mavics.