Originally Posted by Prestidigitweeze
Then you don't find yourself traveling extensively in places where you might not be able to recharge easily. Many of us do, and for us, being able to switch to a second battery, or choosing a higher capacity battery for primary use, is quite important. Being able to do a hard reset by removing the battery briefly can be important as well.
I have tried extra battery for previous phones but they are very inconvenient because you have to reboot. It is much better to buy an external battery and use that to charge the phone.