It's probably because I'm a Kubrickian robot with absolutely no empathy, but songs don't give me an emotional response. Nor do, well, just about any form of media. I mean, I form an emotional attachment to them, but media, and most especially fictional media, doesn't make me feel.
I mean, I'll acknowledge mood, but emotion? Just not in it for me.
In most music I tend to think of the vocals as simply an instrument. A bit of pleasing melody that works well. I certainly appreciate songs with clever, interesting, well-written lyrics (c'mon, I'm a TMBG fan) or that are trying to make a point about something (again, I'm a fan of good, non-pop punk and classic metal), but detached appreciation is usually as far as it goes for me.