When you’re sleeping, driving, or in a meeting, you want to know when your house alarm has tripped, but not that someone posted to Facebook or send you an email.
If you use an Apple device, you don’t get that choice. That means you will likely miss urgent alerts. Apple can and should fix this behavior, ironically by taking the approach Google already has in Android.
iOS’s Do Not Disturb mode setting for iPhones and iPads silences alert sounds and vibrations, and it keeps the screen turned off while the device is locked (both from lack of recent activity and when you explicitly lock it by pressing the Power button).