(1) Some or the other kind of Defect was observed in all the cloned Mammals ( Dolly the sheep, though born a healthy offspring succumbed to arthritis). Any such ill-effect in a human offspring could lead to the creation of a "defective" species.
Secondly, there are conservative groups of people who advocate non-interference in the nature's/God's work.And Governments only reflect the will of the people. So, no governments have by far approved human cloning and would probably not approve until guaranteed success is ensured by scientists.
A noteworthy point here is that cloning does not always mean re-creation of an entire individual (person); but creation of certain body parts is also termed as cloning. So, cloning is after all not that deteriorating to humanity considering its positive aspect that it could return limbs to people severed in accidents or otherwise.