Why can't we reset our MMR?

I've been playing since season 2 and started out as Bronze 5. Through all the fuck ups, rigorous matches, afks, trolls, custom games to improve CS and learn new things, my MMR definitely improved. But why should my past still haunt me and effect my match making?

We should all get a fresh start. Isn't that what it means when ladders reset? I don't want to "continue" from where I left off. I want a brand new opportunity to showcase my skills, without having my MMR affect it in any way. Some games have a reset option. Why doesn't this one have it? I hear stories of players winning 10 placement matches only to be placed in bronze 1. Because their past is unforgiving.

MMR is like a GPA. No matter how hard you try to only get A's, that F will always haunt you. Players should be given the option to "reset" their hidden MMR and start fresh.