If you are using the Windows 10 Version 1709 Creator Update, hit the new patch KB4046355 (self description for the FeatureOnDemandMediaPlayer), you will find this with the Windows system for many years the classic media player has been without a trace.
Microsoft did not make any explanation, KB4046355 patch does not correspond to the knowledge base article, want to come to Microsoft may think Windows Media Player is too old, nothing to use.
In fact, the player has long been updated, the latest major version or with Windows 7 released 12.0, Windows 10 inside still the case.
Earlier years, Windows Media Player has also been anti-monopoly organizations eye, that Windows binding it hurt third-party similar products, Microsoft also had to release in some markets without the player's N version.
If you still like Windows Media Player, Windows 10 also leaves a posterior, enter settings - applications - applications and features - manage optional features - add functionality, drop down to see Windows Media Player, can be reinstalled (no new patch You can also uninstall it here).