New Maps

Riot has created alot of good champions and holiday/champion release related game modes but they all go away over time. Why waste all that time creating a new game mode if only to have it as a holiday thing or not even be played again at all; tossed in the trash like the project has already fufilled its purpose? Why aren't their any new maps for each game mode? If they are in production can someone send me a link pertaining to this induction of a new story?

Most of what I see is new skins all the time which I know I, like most other league players love but I believe the game would be alot better with some new maps for each game mode to give more choice. It simply in my eyes would make the game more vastly enjoyable and playable.