That decision basically killed instant messaging for me. I miss it, but there just isn't any critical mass anymore. I could run half a dozen different messaging apps, each one reaching some subset of my friends, most of whom are never available anyway, but the old situation where it was easy to keep in touch with people via chat just doesn't exist anymore.

I think instant messaging also worked better in the PC era, when you knew people were active, "away" or altogether offline.

The messages I want to send or receive with a phone notification are a lot different from the ones people would exchange in the old days of IM.