Why do I have to have my roommates confirmation to change a move-out date?

Our goal is to make sure that everyone stays on the same page! When bills need to be adjusted and/or removed because of move-outs, we want to make sure that everyone is aware of the change that is about to happen. Since each roommate has signed up to use SimpleBills, we want to make sure that everyone is included and no one is surprised by a change to the bill percentage. 

What do I do if my roommates refuse to confirm?