Apple‘s new mobile operating system, iOS 11, introduces some counter-intuitive behaviors with respect to Control Center and the wireless radios.
Tapping the WiFi or Bluetooth toggles in Control Center does not actually turn off these radios. “In iOS 11 and later, when you toggle the WiFi or Bluetooth buttons in Control Center, your device will immediately disconnect from WiFi and Bluetooth accessories. Both Wi-Fi and Bluetooth will continue to be available,” explained Apple in its documentation for iOS 11.
In earlier versions of iOS, tapping these toggles did in fact turn the radios off. iPhone and iPad owners who wish to completely turn off their Bluetooth and WiFi radios will need to do so from the settings menu. According to Apple, disabled WiFi radios will wake back up under certain circumstances: when toggled on, when users encounter a new WiFi network, when the device is restarted, or automatically at 5am.
Turning WiFi and Bluetooth off is often viewed as a good security practice.