Assign an internal key

Hello ,

  I was wondering what is the real purpose of defining an internal key like this :

Data Model = BP, Entity Type = ADDRNO => Prefix $ (where ADDRNO is the address number)

Data Model = BP, Entity Type = BP_HEADER => Prefix $ (where BP_HEADER is the customer number)

( I have  extracted this  from Activation of the Business Partner (BP) Data Model - Master Data Governance for Customer - SAP Library )

I could understand I add a  prefix for the temporary BP I am creating that way I know it is temporary , but why involve the entity ADDRNO  , I saw in table USMD1213 an entry for every object is created  , thank you for sharing your thoughts.