Answer by Joshua Engel:
Why should they?
No, seriously. Why should they? What's so great about intelligence?
Oak trees are perfectly fine oak trees. Lesser kudus are excellent lesser kudus. Przewalski's horses have no interest in understanding how ridiculous their name looks.
Evolution isn't some ladder, with us at the top. We're just one creature out of zillions, all of them doing OK just as they are. There was no special magic that made us what we were when we were; we just happened to be the right species in the right place at the right time. A lot of different factors entered into it: the climate, the shapes of their hips, the kinds of prey available, the relationship between savannah and forest, etc etc etc. Every situation is different and there are literally billions of alternatives.
If there's an evolutionary factor at play in human "intelligence", it's only in that H. sapiens has somehow decided to wipe out its fellow species at a rate 1,000 to 10,000 times faster than the normal rate of it. That is indeed an evolutionary factor that is selecting against them, but I hardly think it's a mark in favor of intelligence that it's causing extinctions at an asteroid-like rate. And it's exactly the kind of thing that can get this species to wipe itself off the earth, leaving the cockroaches and the sea slugs to duke it out in a newly-opened ecosystem. I wish them luck.