Spaei dont have any money to spend on games and ive never had problems with skype
if you dont have money how are you planning on getting a game server in the first place?
and trust me skype is doodoo for teams, since there's no opportunity to chill with your pals or hang out outside of matches. it also drops calls a lot (and its harder to get someone back into a call than into a mumble), and often lags voice when there's a lot of people in one call.
if nothing else, you can get a lower quality mumble server for free, or ask to use a channel in someone else's mumble server, and it would still be more useful and convenient than skype.