Mainly because they don’t have one and never had one. Hard to dismantle something you don’t have. Even harder to do so credibly.
They had programs to obtain a nuclear deterrent. They can dismantle those programs. But they never had the actual nuclear deterrent itself.
You are mixing up "working on opening a bakery" with "having bread". They are related, but not the same.
Mainly because they don’t have one and never had one. Hard to dismantle something you don’t have. Even harder to do so credibly.
They had programs to obtain a nuclear deterrent. They can dismantle those programs. But they never had the actual nuclear deterrent itself.