When using statistical science, living systems are interpreted as abstract categories of data, with only mathematical properties. That doesn't actually represent what conclusions are later made about, though, like judging students with IQ tests and such. A more natural system approach would be to compare how the deterministic model *both fits and fails* to emulate the living cultures it is supposed to represent.
Sometimes what you discover is truly earth shaking, like when you first discover that the active learning of the individuals has profound effects on their survival, and not a matter of chance at all. All living and lots of non-living opportunistic systems too, have active learning behaviors that totally fowl up the abstract rules of mechanistic behavior. Living things just constantly learn new ways to get around the rules... as a way to survive.
That learning behavior is invariably individualistic is the problem for determinism. Whether an observer thinks it's "smart" or not, it's also "directional" not "random". We don't generally use math to look carefully for directional variations, though. It takes algorithms for locating unexpected continuities. People more fascinated with deterministic rules never ask about that. As determinism came to dominate science it became what scientists selectively looked for in all phenomena. That naturally biased the views of natural processes circulated and it shrouded study of individualistic behaviors in suspicion. So what is now an incredibly interesting and highly important "wicked problem": "...why things don't behave by our rules any more…", is still kept from getting either financial or social support, or even being circulated, resulting in a profound bias in our knowledge at a time of global crisis...
When you just ask why natural systems never quite emulate the deterministic theory for them, what you ultimately find is that deterministic theory is only valid as boundary conditions. It's individual natural processes that need to be aggregated to create the local pathways of continuity we observe in actual behaviors. One of the profound conclusions one can draw from that is that nature's behaviors must be "organizational" and not "numeric" at all. Why we still try to explaining them mathematically is the real question. Why don't we show interest in how individual instances quite generally disprove the rules? You could call it just human arrogance or foolishness or attitude, or obsession.
It goes deeper than our values and attitudes though. It seems to stem from a great evolutionary learning disability, that led to our over-reliance on using the information at our disposal for predicting profits. It's the success of that we see evidently took over the evolution of modern society, early in its development, so productive to become "self-fulfilling" as a theory of nature (whether it was balanced science or not). So (oversimplifying here of course) productive people came to believe and treat the rules in their heads as the world they lived in, (..losing sight of how the information they used came directly from individually organized things working by themselves..).
Tied up with that global blind spot in our knowledge culture is also the secret to why people historically created so many highly productive civilizations to only destroy them, as they reached the end of their growth. It appears they didn't know quite what to do when the civilizations they built stopped following the rules they were built with.
So... what else mysteriously *doesn't* follow the rules we might talk about? ;-)