Dedicated hardware skype decryptors were also been available to gov't since ages.
Also, Hangouts is dedicated software only on Android. Its built as plugin for all other platforms, which is much more versatile.
Skype is in contrast - a dedicated blob, that has full functionality only on windumbs.
The day, someone invents Skype-ish feature reduced P2P network, for the sake of stable account handle storing, will be the day when floss VOIP skyrocket.
Majority of todays open solutions share common problem: difficulty to connect to other member from any country in the world.