My older one didn't, really, and in hindsight it was a bit of a signal - the Whys aren't just about getting information (as you of course know) but about practising the back-and-forth of conversation - and that ds didn't was an indication of him not being wholly interested (ie, not to the normal extent) in other people & communication.
He did something else, though, which was entirely to do with information and we've always liked, which is the "Is that because [ds's current theory]?" - but that isn't the same thing developmentally.
So, though it can be exhausting, I'd encourage the Whys