Is there a reason the game can't remember my pregame choices for each champion?

Title, basically. Why does the game default to the runes/masteries/summoners I last used period, rather than the setup I last used on that champion? This wouldn't take much space on the server if it all, and it wouldn't cause champ select to load any slower, at least not to the point where it would be noticeable.

Obviously, it wouldn't always get you what you wanted, but it would significantly reduce the number of times people forget to change their setup without creating a situation where you have to manually change it when you didn't before.

Thoughts? Maybe a comment from Riot?

PS. Dawngate had this feature and that game was in beta.