I thought of this and I'd like Thanos to tell me why couldn't he just double the universe's resources with the Gauntlet instead of halfing all life in the universe?
Because the movie leaves out something from the comic book. In the Comic, Thanos is in love with death (in the marvel universe death manifests itself as a beautiful woman) and whipping out half the universe is his attempt to get her attention, and she shuns him. So you can say, all these people die for one Titan's love for a woman. But since they left that little tidbit out of the movie, i'm not sure if they are going to bring it up on Avengers 4 or not.