Comment 2 for bug 1476851

At the same time, we don't want to just disable the hardware buttons when the device is locked, because they're often used to change volume of the music (for instance) while the device is in your pocket.

What I agree with, is that we should have a setting that prevents the ringer/alarm volume to be affected by volume hw keys while the device is locked (while still affecting media/video/apps volume!). I think iOS, for instance, has this feature.