My DS3.5 very rarely asks why as well. It gives me pause because it seems to me that gifted children would as "why?" as a way to quench the thirst for knowledge. So I start questioning his giftedness even though he's a self-taught reader, can skip count by 2, 5, & 10 to at least 200, and does a lot of simple addition/subtraction in his head.
His questions are generally less broad, and seem to be more a means for figuring something out for himself. For example, last summer he became obsessed with digital clocks. For about a week, anytime he saw one he'd ask what time it was. Within a week he could identify any number up too 100. Obviously a clock only goes up to 59, but he understood the base ten naming pattern I guess. So questioning is more about filling in missing links for his broader discoveries. Maybe it's because he's more analytical and a little less social.
A few weeks ago I just decided to ask him, "Why don't you ever ask 'why' questions? Don't you want answers to 'why' questions?" He looked at me, a little puzzled, and after a moment of thought he said, "I tell YOU the answers." Oh boy! Apparently he doesn't ask because he's already come to the conclusion that he knows more than me.
