What's the use of a screen saver on a cell phone?

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As for me, I rarely use screen saver on my cell. Seems that using it will reduce the battery life. I use wallpaper instead. Occasionally when I feel like it, I will put a screen saver but not for a long period of time. I'm just wondering, if the phone manufacturer should get rid of this screen saver feature since in my opinion, it's not so useful as it meant to be. What do you think? Do you likely to use a screen saver on your cell? Let me know your thoughts.. thanks..