Why isn't mastery looked at for patches?

For example;

1/20 players are in master, the rest float in diamond. (in this case.. he needs to be looked at DESPITE having a higher than average winrate) 2/20 challengers and 3/20 master players.. (obviously in this case Yasuo is in a good spot) 7/20 players in masters (Fiora op? thanks alot KAHN LOL)

TLDR

High mastery players, with no master or challenger players should be looked at. High mastery players, WITH master or challenger players.. might be abused and should be looked at also.

23% pickrate for jarvan, with 5 masters and a challenger.. (top 20)