Google will no longer be updating Android 4.4 KitKat, which was first released in 2013.
The decision was made because the active device count on KitKat is below 1%, and Google wants to focus its resources on supporting newer versions of Android. KitKat devices will not receive versions of the Play Services APK beyond 23.30.99.
This announcement is a reminder that all software and hardware platforms have a finite lifespan. While smartphones can get prolonged support and usability by way of software updates, it is important to keep in mind that eventually, they will no longer be supported.