Why? Because you can. The rules? You MUST answer with a question every time.
Do you like even numbers?
Even numbers are often more convenient aren't they?
but aren't odd numbers often essential?
Aren't all the letters of the alphabet essential?
Why must we place so much importance on what's 'essential', anyway?
Why are you questioning our line of thought?
Are you sure that the thought is a line, or could it be more of a squiggle?
Do you think this has anything to do with Mr Squiggle?
Mr Squiggle lives on the moon doesn't he?
Do you think he gets lonely there?