Another thing to keep in mind is that most phones will display the content of SMS messages on the lock screen, even if the phone is locked. That means that if your phone is stolen, hackers can easily take control of accounts such as PayPal that use SMS verification as the only way of establishing one's identity.
This exact scenario happened last week to a friend of mine, I wrote a little article about it: http://gregschlom.com/misc/2017/01/29/hacking-paypal-account...