It makes sense that Superman is so stupid. Stupidity is probably what's going to get us super powers. After a few more generations of wandering in front of trains and spilling hot coffee on ourselves, we'll evolve to give birth to invincible babies. As long as people know how to make plane reservations and use a stove, we'll never learn to fly or shoot heat beams from our eyes.
Helpless idiocy is the key to the future.
Superman moves the Earth around a lot, and whenever it happens, we see a shot of it from space. He flies away from the camera, disappears into the distance, and the Earth starts moving. But to anyone standing next to Superman at the time, it would just look like some guy in pantyhose was doing a handstand. No, you'd run like hell and call the handstand police to give them the case of their lives.