y Rv* Programs get overwritten in upgradation?

For User exit includes which are reserved for User Modifications, SAP does not release new version for such programs. So includes of this nature are not adjusted during modification upgrade.

But we have some RV* programs like RV45PFZA, RV60AFZC, RV60AFZD, RV60BFZA which are reserved for User modification.

But After upgradation we found that such program are overwritten by SAP and all are present under SPAU.

What can be the reason of it?

Regards,

Umesh