I'm guessing that you have turned wi-fi and Bluetooth off in Control Center. If that is the case, it has changed how it works. To turn them off completely, you must use the switch in Settings. This is a change by Apple. See this, Use Bluetooth and Wi-Fi in Control Center with iOS 11 - Apple Support
Having Bluetooth and Wi-Fi on will not adversely drain the battery. I keep mine on all the time.