"I just dont have time for that mom!"

Since when is it okay for my child to respond to a demand I make of him in a way that I am being bossed around? I will ask him to get dressed, to blow his nose, to clean up his room, to read to his sister, or you know, the everyday stuff... And I will get a response like this; "I just don't think I can" or I don't really have time for that right now" It's not even in a snotty way or rude way. It's in a nonchalant way with the shrugging of the shoulders and the look of "there's nothing else in the world I can fit into my schedule" kind of look. So innocent yet so matter of fact like he knows exactly what he wants to accomplish today and if I load one more thing on to his schedule of playing, he might just die! Wow I don't know what it would be like to have to fit that many things into my busy schedule,how do those 3 year-olds do it???