WHY CAN'T WE CHANGE RUNES IN GAME

Hey everyone, I have a question that we've all wondered but have just let slide for** YEARS** now.

If we can change our masteries while in a lobby before the game starts, why can't we change our runes? rune pages are expensive and a lot of people only have two, (one for ad and one for ap) and I would assume that everyone has more than two champions. I don't like every champion of the same damage type (physical or magic), with the same runes. For example, I take mana regen seals on Viktor, but when i play Akali those seals are wasted. And i don't always have the time to change runes between every game. If this was implemented into the game, I along with many other summoners would be very happy. If this is possible I think it would be a great addition to the game's current state. Masteries are a bit different, not only are they free, but you get 20 free slots to put them in, and can be edited in lobbies. Tell me what you guys think about this and answer the poll on wether it should be in the game or not.

Thank you for your time,

Beast from da East