Not sure about other parents but I am not getting tired answering all the "why"s to my 2 years old :) We try to teach in a way of always giving options of actions so that child felt she has a power of decision.
But also from child psychology we know, that small child feels unsafe if she does not know boundaries, what is allowed and what is not - here comes the mandatory parent control for child to feel safe and his brains to develop normally.