As far as I know most people use Skype for business calls. Maybe "team communication" was something that can be done with Skype, but I don't really think it's their core focus.
I think what them not buying Slack is implying is that they will start to try and actually compete with Slack directly. Instead of just internet telephony.
It's also used for video games a lot, but between leaking your IP and allowing esports players to get DDOSed, and just generally being not a great fit, Discord is getting more popular.
I think what them not buying Slack is implying is that they will start to try and actually compete with Slack directly. Instead of just internet telephony.