but I can use it offline with any software I want on any device whenever I want
Tell that to all the VCR tapes in people’s basements. Finding a working VCR player is nigh impossible these days, and it won’t be too long until optical media is the same. Last car I bought didn’t have a CD player. DVD drives are disappearing from computers. Game consoles a generation or two from now will be download only.
Content owners can’t wait until the only option we have is to stream.