If the bad guy is close enough to count my rounds I'm really screwed. And I probably deserve to get shot. I seriously doubt that would ever be an issue. And since you should be pointing your gun at the bad guy, all he'll see is the leading edge of the magazine, and that's not much. Chances are he'll be looking at your hands or eyes, not at your magazine.

And if I have time to look at my magazine, I better be behind cover.