Bans in ranked and draft

When ranked and draft began there was a much smaller pool of champions than there are now, yet at the time 3 bans per team was chosen as fair. Now, with more than double the number of champions in the game, I feel there should be 4 or 5 bans per team to keep up with the number of champions that there are to take into account.

I don't play much ranked personally, and since the removal of team builder, I'll be playing draft more often in the future, but it makes sense to me to increase the number of available bans. Anyone have any feedback on the idea, or any reasoning as to why this hasn't happened yet? I'd appreciate the take of someone who maybe plays primarily ranked or draft.