I think that is a very appropriate question, one that is often asked of members and one that Chair occupants also have to ask themselves.
The reason is the authority vested in the Chair to maintain order, decorum and the smooth running of the affairs of the House to assure that all members of the House are given respect and the opportunity to make their case. It is also to ensure that at the end of the day the affairs of governance are concluded or are able to reach conclusion in a fair and orderly manner. The authority is not necessarily vested in a particular statute. The authority is vested in the Chair after 500 years of parliamentary tradition.