Why Autofill?

I just want to know why I have to have auto fill enabled when i play ranked. I get it wil make queue faster and all taht but I would rather wait 5,10, even 15 min longer if it means I get to play one of the roles i selected. I don't want to wait for a game to play support that I don't play and then get stuck with it because none of my other teamates plays support cause Im supposed to be the support player. I don't find it fair that I grind and practice to climb in ranked and give it my all when I give my team half my potential as playing support. I don't find the role to be my style and doesn't make the game fun for me. I would much rather just not play the game instead of haveing to support in my ranked games. Its not fair to me or teamates. Riot has disabled auto fill automatically in promotion games so they obviously see that giving people their desired roles is gonna be the most beneficial in the promo games so why not treat the games up to the promos the same? Are they not as important as the promos? I just loved teh last season when I could at least gurantee a role I at least practice and be competitive with.