The answer to this Pacific Standard essay is, in my view of things, quite simple: For the same reason we keep asking "Why" in the first place: The need to question.
It is precisely why one of the main tenets of Cosmolosophy is the idea that the entirety can be thought of as an unimaginably immense question answer engine. An iterative process where the output forms the new input, and thus, more fodder to continue on indefinitely.
This essay, though, adds some lovely perspective to the underlying elements and I do recommend giving it a read, especially as it relates to preliterate times and how literacy gave us a sense of linear time; something any serious student of Marshal McLuhan would recognize immediately.
For my part, however, I think we were questioning things well before we had literacy, though probably not before we had established languages. Language itself, in my view, was a critical component in allowing for full sentience, as it is the very fact of objectification that gives us not only sense of the difference between inner, and out experience, but a sense of self in the first place, as well as a point of specific reference with which to experience from. You need only check out this other recent essay in Nautilus to understand just how important language is in that regard.
This is also why Mind, as well as the Elemental Embrace, form the two essential processes that make up the unimaginable question answer engine. Without mind (or meaning processor) there would be no objectification, and thus language, in the first place. As well as for there to be something for everything else to be relative to.