If the members gained control to edit polls the options would be extremely restrictive. In the case of just editing the questions and title, along with that power comes the ability to change the amount of votes for one of them. If a member for say had an art shop and put a poll asking how good people think their artwork is, they could edit the votes for the best option to be a number like 200. They could also remove bad votes.
So if we did this it would have to be extremely restricted and to the point where it would be no fun.