You might not agree, but no, you don't need them. Its a sign of no confidence in the quality of the hardware you've chosen that you implement a feature - and make it normal - like a battery status indicator.

The mobile OS should be intelligent enough to (a) let you know when its at a point where the battery technology its using needs to be topped off; (b) stop running tasks at low usage times of the day, or learn when you aren't using your device (like when you are sleep and going into an extreme power saving mode); and (c) to let you know in daily, weekly, or monthly summaries in your notification panels that your methods/behaviors of use summaries and recommendations to improve device/service performance.

I've written twice before on antiquated features in modern mobiles (here and here); the crutch that folks have for those features hold back what we can be doing better. If your mobile was so smart, why are you spending so much time learning it... shouldn't it be learning and adapting to you?