I love this explanation. It works so well.

Quote
"There can be no Utopia without your children, that is, the natural children of you and Ms. Lane."

Clark flushed and looked away. "Then there isn't going to be a Utopia. We can't have children."

"Not in this future, no. But in the past, with Mr. Luthor dead, there is no one to stand in the way of you and Ms. Lane marrying. And, if you are married prior to the New Kryptonians arriving on this planet, well, they will not compel you to join them. In fact, they will abandon this planet and you as lost causes and move on. When your people placed you in that molecular disruptor, Mr. Kent, you were temporarily, uh, disrupted. Yes, the process was reversed, but not everything was entirely restored. Were you never to be disrupted, you and Ms. Lane would have been able to have children."
What a shock for Clark - to know that once, he and Lois could have had children. And now, they can ... in another time line.