You see, so what stops them all from implementing their clients and servers using conformant XMPP with enabled federation? Can your Facebook messenger connect you to users of WhatsApp and vice versa? No. With Federated XMPP it'd just work. Is it just their greed, or lack of thinking? Actually Facebook does use XMPP, and I think even WhatsApp in some way internally does, but Facebook server lacks federation, and WhatsApp isn't even conformant to standard XMPP. In the end - you have no way to connect the two.
This situation resembles the early period of the Internet, when users of Compuserve couldn't send e-mails to users of AOL (and other way around). It sounds completely weird today, but how is this situation with IM networks different?
Understandably there are historic isolated networks (AOL, MSN etc.) which predate any serious federation efforts, and even they are slowly enabling XMPP in some ways. But creating new closed ones in the present time is just weird and only serves to make the situation worse.
This situation resembles the early period of the Internet, when users of Compuserve couldn't send e-mails to users of AOL (and other way around). It sounds completely weird today, but how is this situation with IM networks different?
Understandably there are historic isolated networks (AOL, MSN etc.) which predate any serious federation efforts, and even they are slowly enabling XMPP in some ways. But creating new closed ones in the present time is just weird and only serves to make the situation worse.