No and while your reason for suggesting this is I'm sure in the best interest of the world, it would cripple users abilities to do certain things on their phones if it was made a permanent option. The purpose of low power mode is to prevent the phone from dying when you aren't in a position to charge your phone, but can't afford to have your phone shutdown. As such it reduces the load on the battery and stops some features from running to conserve power.
That said, finding ways to do things using less power, while maintaining a phones ability to do everything it was designed to do, is certainly altruistic and maybe one day, they will learn how to make phones use less power and last longer. The technology isn't here yet.