It has to do with the screen display esp those with big touch screens, which consume a lot of power. Coupled with those lousy korean batteries, you can expect to charge you phone every 1-2 days. Make sure you set your phone to shut down the display say within 30 seconds if there are no activity so as to preserve battery power.
All mobile phones are lousy these days. I have to carry at least 2 in my pockets everywhere I go. Just in case one dies in the middle of an emergency. And both phones are junk and have to be replaced every 6 months.
some phone os's preserve battery life while some don't. also, some apps are always on and they drain battery life. besides larger screen size which drains battery life when they're lit, there's also the camera flash. flash drains battery life the fastest.