Jabber implementation

Considering that the future is for Jabber, I often wonder: why are Jabber services not integrated with Web (-2.0) services?

When the Jabber server was opened in LiveJournal, I was sure that it would allow receiving notifications about new posts, comments, and so on. And, of course, I was very surprised when I didn’t find anyone there but the goat Frank.

And I would like to see such alerts on almost all more or less large web communities.

The advantages, in my opinion, are obvious - getting information about new topics, posts and comments instantly, within half a minute (remember, how often does your aggregator update the tape from Habr?)
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I see one major flaw - receiving messages at the wrong moment (distracting at work, received a lot of messages during absence, and so on). But this is, first of all, the status of your presence (for example, if not Online - messages are not sent more than once per hour). Secondly, you can implement the daily routine - for example, so that you can set in the service settings a ban on sending messages during working hours more often than once every half hour.

Maybe I globally missed something, and it has already been implemented?
And if not, then there are probably some big pitfalls here?

And more specifically, I want to see such a service integrated into Habr.)