I respond to your guestion for the fairness sake, but my reasons are not impressive.

1. Most of it is probably a wishful thinking, driven by my desire not to have the powerful AI aronud. I am scared at the idea.
2. The fact that people have felt AI is near for some time and we still do not have it.
3. Maybe the things which are essential for learning are the same which make human intelligence limited. For instance forgetting things.
4. Vague feeling, that biologically based inteligence is so complex, that computers are no match.