Why? Apparently because if humans are the exclusive repository of reason then that would make us special and human specialness is much more compatible with a theistic worldview than with the naturalistic worldview Smith is eager to defend:
In answering the where question of reason in this maximally broad way, we are able to preserve the naturalism that philosophy and cognitive science insist upon today, while dispensing with the human-exclusivity of reason. And all the better, since faith in the strange idea that reason appears exactly once in nature, in one particular species and nowhere else, seems, on reflection, to be itself a vestige of pre-scientific supernaturalism....In order, however, to argue that reason exists everywhere, a kind of panpsychic view of reason, he has to adopt what some might think a rather tendentious definition of the term. "What if reason," he asks, "is not so much an inferential ability, as simply the power to do the right thing in the right circumstances?"
In other words, reason may not involve deliberation at all on Smith's view. It's simply a reactive, reflexive process that everything in nature possesses or is capable of. This is surely a strange definition. If reason is the power to do the right thing in the right circumstances then a rock which falls to earth when released is exercising reason.
Smith makes the point clear in this passage:
Potentially, it’s not just living beings that fall under the scope of this alternative interpretation of reason as the power to move directly to action, rather than the power of making the correct inference. For everything in nature also just does what it does, simply and without deliberation, by virtue of the fact that everything in nature is bound by the same physical laws.Smith's odd definition actually empties the word reason of any real content since everything that happens would be reasonable, and if reason is just the way things happen then what need is there for the word at all?
Nature just keeps working smoothly. It never, ever breaks down.
Nature itself is a rational order, on this alternative view, both as a whole and in any of its subdomains. Reason is everywhere, with human reason being only an instantiation or reflection, within a very tiny subdomain, of the universal reason that informs the natural world. So perhaps it is also time to give up the idea of rationality as nature’s last remaining exception.
In fact, though, reason is usually understood to be the faculty by which we consciously engage in abstract thought and by which we comprehend that about which we are thinking. Only human beings can do this, and that makes us unique, perhaps unique in the entire universe, a state of affairs repellent to the naturalistic worldview of which Smith is an enthusiast.
If he really believes that reason is just the power to do the thing which, in the biosphere, enhances survival then one very troubling consequence for him is that no one has any justification for thinking that reason can lead them to truth. After all, falsehood can as easily enhance survival as can truth, and believing and pursuing beneficial falsehoods would be rational.
Harvard's Steven Pinker echos many atheist philosophers when he writes that, "Our brains were shaped for fitness, not for truth. Sometimes truth is adaptive, sometimes not."
Why then does Smith bother to write an article to try to convince people through an ostensibly rational argument that he's right? On his own terms reason doesn't always produce truth, it's merely doing the "right thing in the right circumstances," and his essay is an exercise in pointlessness.
The need to deny human exceptionalism because of its uncomfortable theistic implications leads naturalists like Smith to embrace some pretty bizarre notions. The idea that reason is ubiquitous and universal in nature is surely among the most bizarre.