iphone battery sucks. i barely use it and i have to do a full charge almost everyday. i always close the apps.
My battery lasts a good nine plus hours
plus, im sure people charge their phones overnight, and when you charge it like 8 hours instead of the recommended 3 hours. then you overcharge your phone, in which, kills your battery and then eventually your battery life will only last a little while. also having an intense amount of apps on your phone kills your battery too and keeping them open.