Scope.
Imagine we both live in the US. I show you an article about an immigrant raping someone, and you say something like "well that's just one guy." I show you another, and another, and another. I show you a thousand. I show you ten thousand. Either you eventually admit that immigrants are predominantly rapists, or you look increasingly, ridiculously, obviously, wrong. And stubborn. And irrational.
But you are not wrong. I am wrong.
Because there are 331 million people in the United States, I can find an inexhaustible supply of immigrant-rapist stories.
Now take that inability to grasp large distances, large quantities, long periods of time, and apply it to everything. This is why young earth creationists exist- because a billion years is literally unimaginable. This is why people play the lottery- because you're saying there's a chance, right? This is why we don't react emotionally upon hearing of a genocide, or learning that 70 billion animals are slaughtered each year for meat.
We are not equipped to function at the scale that we are currently working at, as a species. We have been haphazardly constructed by evolutionary pressures to operate in small bands and villages, and we do not have the appropriate intuitions for any scope larger than that.