• Right now I cannot send text directly to your instant message account (unless you’re using an XMPP-based client), I have to send the message to your IM server which relays the message to you.
• I cannot send audio directly to your phone, the phone company has to route it there.
• I cannot share a picture directly with your Facebook account, I have to sent it to Facebook first to be carried on to you.
• I can’t send a file directly to you, I have to put it on a share or email it to you.

XMPP removes these intermediaries from the network.  Social networks and proprietary transports no longer have an exclusive license to deliver content, the clients talk directly to one another.