At my current work place, Skype and Lync (or Skype for Business) are what we used for team communication. It works great until we need to onboard/offboard people. I also need to set status to DO NOT DISTURB because I wanted to avoid the constant ding ding ding notification.
At a previous workplace, Skype and IRC are used (IRC are for mass communication, whereas Skype is more for personal-level communication).
Since so few people use skype, everybody else has little motivation to use skype, ad nauseum.
Honestly, the only people I've seen that use skype are recruiters. Other than that it seems pretty much dead.