The &#x27;other&#x27; possibility is that hard instances have &#x27;measure zero&#x27; in the space of all instances...  So when you pick some random problem in the real world, it ends up being relatively easy to solve with high probability.<p>My feeling is there&#x27;s a bit of each; the problem space has a bit of unknowable quasi-structure, and also tends to miss the perverse corner cases and counterexamples that we like to think about as mathematicians.