Earlier quoted context omitted.
Because the NSA pays them to. Why did they do to Skype what they did (first turn it from p2p to centralized and spyable and then just ignore it and let it die)? Same reason.
(Opinions are my own, I have no inside knowledge.) I vaguely remember hearing that P2P Skype was the bane of sysadmins' existence. Skype would elect clients on high-bandwidth networks as supernodes. This tended to be business customers - the very organizations MS wanted to attract. Skype's prodigious hole-punching ability made it difficult to throttle, so it got banned from a lot of enterprises. MS essentially hosted…
I used to leave an extra old laptop on with it running, maybe 15 years ago, on a public address.
During the arab spring, tons of traffic could be seen connecting clients in north africa. It truly did route around things.