With this phone, I'm forced into an environment where I feel like I need to be social all the time, and I feel that might wear on a lot of people.
I think the younger generation doesn't have an expectation of non-invasiveness yet. They just aren't doing anything important enough to be bothered when interrupted. I think that changes when you get a little older.
I'm 27 and this rings true for me. I use to have IM enabled all the time, and work on some things in the background.
That's no good for things I'm doing now, and I rarely chat idly on IM.
With the exception of Facebook Chat, that is the purpose of the Online status. There's (busy/your client's name for it) for "I'm here, but may not be able to reply". And offline for when you're actually not available. If it wasn't for Skype's terrible offline messaging implementation, I'd have said that 90% of the time offline or busy implies you should probably close the IM client.
(Facebook is different because afaict, there's no way to manually put it into the away state, it just does it if you haven't interacted with Facebook in a while)
I think this was probably a user story for them and definitely one of their biggest motivations, unfortunately lol.