Its a dumb phone, you insert a sim card and thats it. The telco will know where you are based on the sim connection to towers (as with any other phones) and all calls and texts are stored, but other than than you dont have to worry about anything else. I suppose you dont have to login to some account to make it work therefore even if it harvests any data, it does not know who it belongs to (no add ID) so not saleable. Its pretty easy, no real identity (through email, account, etc) attached to it = private.
Do you really not have prepaid sim cards in the US? that you buy with 5 bucks and it lasts one year, and then you just top it up for another 5? Those carriers are really milking you good over there.