Weekly Free Champions

Okay so I know champions are selected for free champs to an extent of having balanced champs. Just as a suggestion, I was wondering if anyone had thought about adding more difficult champs (such as etc.) for more seasoned players. I know a lot of it is geared toward new players learning the game, which is great, but wouldn't it be good to split it up somewhat so that seasoned players can benefit from this too? I know these champions for example get put into the free weeks, but it's rare whereas some easy champions may go up 3-4 times before we see another champ again such as . I just didn't know if there was a reason behind this that I might be missing. Thanks!