This is how the XMPP protocol as been designed.
It is very powerful and most of all extensible, most likely thanks to the use of XML.
If something is not in the protocol, you can add it for your own need.
It is implemented in the server for multiple things, including pubsub and multi-user chat.
You shouldn't need to address the recipients, presence already involves people subscribing to your "presence channel". Thus your homeserver should know how to distribute the efficiently - for example by multicast. XEP-0033 just adds redundancy.