I don't use github or linkedin. I don't use skype either... because Microsoft ruined it and everybody left (for business now I use Hangouts and for gaming now I use Discord).
Everyone I know quit using Skype too.. it's tough to have this argument without access to expensive market research reports, though
More anecdotally, the only time I used Skype in the last few years was when I had a remote job interview with LINE. (Ironically, LINE's core product is a Skype competitor, and they refused to use it for the interview even though I said I'd rather stick with LINE and not install Skype. If that isn't a red flag, I don't know what is, haha)