Find my iPhone is one of those very useful features that you want to have turned on. It can prevent a thief from erasing your iPhone, or it can help you locate your device. It also lets you erase it remotely, lock it, or simply send an alert.
As long as Find My iPhone is turned on, you can’t erase your iPhone. There are times when you will want to know how to turn off Find My iPhone, such as when you’re getting ready to sell your iPhone to trade it in for a new iPhone 8 or iPhone X.