I cannot say for sure but here are four things that cones to mind: - Considering how much of a problem normal space debris is I'm happy we don't have a number

I cannot say for sure but here are four things that cones to mind: - Considering how much of a problem normal space debris is I'm happy we don't have a number of old nukes in orbit. - I also guess nuclear weapons need some maintenance. - Leaving nuclear weapons in orbit would make it possible for another country to try to intercept/study/disarm them. - Regulations/treaties about weapons in space