Assuming there is a soul... and assuming souls have an influence on people, presumably on the brain(?)... then there would be a natural and physical (therefore observable) effect or result on the brain with no natural cause. This is not what we observe.
One might try to impose the idea that consciousness is a direct result of the soul. But if this were true then the brains of infants, amnesiacs and victims of brain trauma would be on similar consciousness footing with custodians of "normal" brains. This is not what we observe.
And if there were souls wouldn't they (therefore "we") have a much clearer picture of the nature of the supernatural realm, all things spiritual, the nature of deities and the afterlife? Yet what we observe is many disparate supernatural belief systems. Culture seems to be a bigger influence on supernatural expectations than any commonly held unseen informed "soul."
What we do have in common is the ability to identify the agency (consciousness or intent) in people, animals, plants, fire, gravity... This is a great survival tool. It allows us to make predictions. Though we might not always predict correctly we can make partially informed decisions. And we usually chose what we predict is safest or most satisfying.
Animals, plants, fire, gravity, etc. all have behaviors, some more predictable than others. But do abrahamic adherents suppose these things have souls? I am not suggesting these things do have souls. We are very similar to a great deal of the animal kingdom. Physically, what most separates us from the animals is our neurophysiology.
Our fore-brain activity, predictive thinking, organizational assessments, pattern recognition, imagination... make us distinct, arguably "special" on Earth. Do we have a more "special" neurophysiology because of our un-observed souls? Or do we have un-observed souls because because of our "special" neurophysiology? Or does that neurophysiology allow us to believe we have souls despite a lack of any objective informed reason to do so? Or maybe it is just a coincidence that only humans have both souls and imagination.
The neurophysiology of the human brain does not require a soul to explain its functionality. Subjective experience, fear of death and wishful thinking may make the idea of an eternal soul so appealing that confirmation bias will overwhelm reasonable and objective skepticism. If someone has any objective evidence of a soul, by all means, let's take a look at it. But if you want to present a cosmic conspiracy theory about why souls exist but can't be observed, I already have a shelf full of fiction I've been meaning to get to.