Many years ago I became annoyed that my hotmail account let it be known when I was logged in.
I would be busy trying to catch up a bit on my emails during the few minutes I had before I needed to leave for my job.
At times a pop-up would appear from a friend that didn’t have a pressing engagement wanting to idly chat.
I had the choice to ignore and risk offending the friend or abandoning my intended goal.
Anyway, years later when I joined the SitePoint forums, one of the first things I did was to hide my online status so as to not be interrupted.
Later, when I became Staff, my Team Leader pointed out that I should consider making myself visible so that members could contact me via PM if they had an urgent problem that I might be able to help with.
I can’t speak for others, but as non-Staff if I want to chat I’ll chat.
If I’m busy reading or putting together a post, I want to not get interrupted.
Selfish perhaps, but I’m not always up to, nor in the mood, for multi-tasking
Different story as Staff though