Why should teamates in ranked be allowed to ban already pre locked champions on your team?

This happens to often and can get super annoying. But the people who do it get no backlash, this goes for people who troll ban your pick and just act like nothing is wrong. They should at-least add a warning or remove banning already selected picks on your team in ranked it would save many people the frustration of dodging or playing champs they may not fully enjoy. And I know that trolls could auto-lock champions that would be good bans but still it would help people more than not and stop mistakes.