because i don't want to carry an external battery AND a microUSB cord to the club and everywhere i go! and i dont want to have to worry about keeping it charged and remembering to carry it! this is for EMERGENCY situations to get you a couple of hours of talk/data time. you are really missing the obvious use case here. have you ever been out at the bar or club at 3am and your battery died? or wake up hung over in some strange chick's house at 9am miles away from your house and a charger?
because out of all things, you're going to have a 9 volt battery handy in your pocket?
AA battery uh maybe. 9 volt?
People don't even have 9 volt batteries at home to change their smoke detector batteries, how are you going to have a 9 volt battery at a club?
As far as any of those incidents happening, I have a wife who always happens to have a rather large purse full of snacks, candy, and an external battery charger (i.e. like the Anker one I posted above.) So, no, I have never come across a situation particularly due to the fact that you would require a rare, expensive 9 volt battery. Have you seen the price of those things? they're like 5 bucks. Eff that.