Re: MAN OF STEEL - Grading & Discussion
Really, saying the Kryptonians having had other colonies leaves too many "Yeah, but...." questions in place while also mudding the "Last Son of Krypton" thing. I more like the idea that Kryptonians couldn't leave Krypton either due too high of gravity for meaningful space travel to be possible (Kal's ship being the exception as it was launched as Krypton imploded thus didn't have to fight gravity as much) or it was a banned practice as Kryptonians knew how different types of solar radiation effected them and the implications that could have on other worlds.
Here it's like, "Yeah, we did it. But gave up. Everyone else out there? Who knows what happened to them? NBD."
They hinted at the reason both with the inclusion of the Phantom Zone prisoner/scientist Jax-Ur and by showing Krypton's destroyed moon Wegthor, which he blew up. That was what ultimately prompted the Kryptonians to give up space travel.
My name is Ozymandias, king of kings: Look on my works, ye Mighty, and despair!
Nothing beside remains. Round the decay
Of that colossal wreck, boundless and bare
The lone and level sands stretch far away.