Yeah, the lovely Roxy once again cuts through the crap and gets to the heart of the matter. It can indeed be that simple. Why don't they talk about X? Cos they don't have any interest in it. Generally speaking, it would seem pop stars are not the type of people you expect to be very well educated in political or social issues. Remember that bastion of social awareness and political opinion, Britney? "Well he's the president so we should listen to him." Yeah. Says it all really.
This is a lot of why artistes working outside of, let's not call it mainstream or current, as that is just getting misinterpreted and could cover so much more, let's say pop artists, tend to tackle these issues. The artistes I and others have mentioned are not totally concerned with chart performance, airplay and pleasing sponsors, and know they can be more controversial in what they say because sometimes that's why their fans buy their music.