The main problem with chat is that there are too many angles to communication, making it impossible to fulfil all requirements with a single tool. Apple does IM, period, they don’t want any of the Slack-type team communications and that's fine for them. Even Facebook realised that having multiple chat apps is fine as long as they offer value on their own. Meanwhile, Google has gone through several iterations, with internal groups competing for the top spot in defining what a chat app should be, but ultimately falling short because there's no single chat app for all requirements. They aimed too close to the average and failed to deliver anything useful enough for any specific group.