this is a clickbait, and nonsense, there are scenarios (like field use) where phone is simply too delicate to serve as a power bank. Not to mention that it drains in no time. Unless you turn it off to use it as a power bank. In which case, you compare its price with that of a power bank and start wondering: wtf did I read this (...)? :)
I got a 10000 (ten thousand) mAH battery for my galaxy note 3. (Ref zeroLemon batteries) that ended when removable batteries ended. Now we are back to 10000 mAH batteries.