Well that's probably at least in part because a major motivation for that acquisition was not to actually improve the underlying technology. To quote verbatim one of my favorite hn posts of all time (https://news.ycombinator.com/item?id=18411779):
A series of headlines:
2009 - NSA offering 'billions' for Skype eavesdrop solution [1]
2011 - Microsoft buys Skype for $8.5 billion. Why, exactly? [2]
2012 - Skype replaces P2P supernodes with Linux boxes hosted by Microsoft [3]
2013 - Microsoft handed the NSA access to encrypted messages. Subhead: Skype worked to enable Prism collection of video calls [4]
1. https://www.theregister.co.uk/2009/02/12/nsa_offers_billions_for_skype_pwnage/
2. https://www.wired.com/2011/05/microsoft-buys-skype-2/
3. https://arstechnica.com/information-technology/2012/05/skype-replaces-p2p-supernodes-with-linux-boxes-hosted-by-microsoft/
4. https://www.theguardian.com/world/2013/jul/11/microsoft-nsa-collaboration-user-data
Interesting. I did some work overseas in out of the way places - did supernodes used to be potentially very close to you if you had your own network that was limited back to larger internet?
Potentially yes: the supernodes were just other "regular users who had sufficient bandwidth" which could be quite efficient if you were all in, say a remote region with good local bandwidth but little connection back to the rest of the world. Obviously though, this P2P structure would make interception of message content by Skype corporate rather implausible! There's a pretty good figure and explanation in the ars article above.
