Hi,
Enhancements are applicable when you want the existing program not to loose its functionality but behave little differently as per your need. When you enhance a code, SAP tables keep track of every enhancements done in standard programs, so that if you are upgrading your system these enhancements can be tracked and can be examined.
When you copy a standard program with enhancements SAP will not be able to keep track of these enhancements. Hence they will not be able to help you during upgrades as they cannot find these enhancements. SPAU and SPDD are two transactions that let us know if certain enhancements will be troubled or not. with copied enhancement they cannot determine these points and hence there is no outcome for these.
As Swanand said you have to copy the implementations into your code. rather than coping them as enhancements.
Regards,
Vishal
HAPPY ABAPing