If I took a few minutes to think about it, I could come up with at least a dozen ways to achieve this.
Personally, I do care about this "feature" since I do not turn my earphones' volume high enough to worry about others being able to hear what I am listening to when I remove them. When I do crank the volume higher than usual, it is usually because my surroundings are at least that much noisier so I still would not need to worry about being heard.
I suppose it is a perfect fit for those people who blast their ears so loud you can hear their music across the hall in the bus/train/subway/restaurant/etc. - spare them the trouble of pausing their music when people interrupt them to ask to turn it down because it is so freakin' loud.