That is a rather effective short answer. Just in case any explanation is needed, for the OP or anyone else who comes in to have a look:
Having a child depends a great deal on natural law and free will. God set natural law into motion, and then set down a certain set of rules for us so we can best experience that natural law - e.g. getting married to have children. However, with our free will, we’re free to interact with natural law outside of those rules. If one could only have a child by being married, then it would be a form of coercion, forcing people to marry in order to have a family. While you or I might not see it as a big deal, there are plenty of people out there who would feel slighted if that were the case.
In relation to this, one might ask why God allows children to be born as a product of rape. I think it’s in this situation that one might see exactly why this happens. Rape is a terrible thing, in every way. But it is a real miracle when a child is conceived by it. That child is not just another part of the curse of rape (despite how some people would like to paint it). God takes something bad and makes something good out of it. The same could be said for willing couples. While pre-marital sex shouldn’t be compared to rape, they are both sinful, and as such are both bad. But both can be taken by God and turned into something good - a child.
I think it’s for this reason that if cloning does carry on and is one day successful, it will be because God - though maybe after a long sigh - will respect man’s free will and cooperate by providing a soul.