Changing an article status in MM46

Good Day,

When changing an article status in transaction MM46 from status D (DISCONTINUED) to M (MANDATORY) the system gives the error:

There are still open purchase order items or scheduling agreements

I have tried to manually change the status in MM42 but I get the same error.

Why would an article status change only be allowed when there are no open PO's and Scheduling agreements.

I understand the impact of changing profit centres and there are open orders/

Regards

Lindsay