Some people used AIM like this as well, at least I did. I left my computer on all the time, so I was always online.

I was in college during the peak of AIM and it was useful to know who was at their computer or not, which I believe was still viable. Around meal times, we could quickly scan for who was around to see if they wanted to head down to the cafeteria. If they weren’t around, there was no point it asking. For time sensitive messages, online status matters.

AIM also had useful states. If you were away for a decent chunk of time (And you could configure what that amount of time was!) it would mark you as idle, and you could set custom away messages (That were actually visible) so folks could know why you were away, or more realistically, what song was on your mind.

Nowadays the status is completely meaningless. It's a small dot that doesn't accurately reflect your status, and if you choose to set a message, most of the apps hide it anyway.