How about when a weak goon retreats, sits around a corner, and takes you out before you get a shot off upon coming around? But you see that he's got 40 hp left, which you could not see any other way. This is pretty common really. I'd say it's even more important when discussing a human who shoots a dretch from far off, but the dretch gets to know his hp. You're thinking too much on direct battles that end with one dying and the other being hurt. It's a bit deeper than that, and I could post quite a few other example scenarios, if they weren't obvious.
Sure, it hasn't been abused, and yes, MAYBE it helps the newer players out a bit. But c'mon, you've gotta be retarded to not realize what it means when an alien or human makes certain noises. That's something you probably learn in a day. Basically, by its current use, this feature is practically useless except for telling someone, "Damn! You only had 1 hp?"