new champ selec question

Why are there people who hate this with a passion.. This one game I was in my teamate banned a champ somone on my team wanted to use and he went into an uproar. BUT that has happened to me befroe. someone will say "please don't ban X' but they do it.. Besides that this gets ride of the "mid or I feed" you pick two lanes you are good at and you should get one right? so what the heck is people's problems?? I don't understand