Well, first of all, I'd say that God doesn't create "non-Christians" -- he creates people, period, and endows them with free will. And some of those people choose not to believe in Him.
So your question becomes, Why does He bother to create the people He knows will choose not to believe in Him?
One reason is that even those non-believers have roles to play in the history of the world.
Another reason is that some of the non-believers' descendants will be believers. And God is not willing to cancel the lives of the descendants who will be believers simply because some of their ancestors will reject Him.
That certainly makes sense, although not very good for those Non-Christians that He knows don’t have a chance of going to heaven.