Licensing bullshit
https://www.reddit.com/r/Windows10/comments/8ptbss/comment/e0dv1d4/?context=3
https://www.zdnet.com/article/if-vlc-can-ship-a-free-dvd-player-why-cant-microsoft/
Explains it well.
Tldr: VLC is in France and doesn't have to respect copyright laws over software while Microsoft does and has to pay money for codecs per install.
It went up to 200+ in the first week.