Since I work at a commercial gym, where most workouts consist of back & bi days and the like, I often get the question, "What does that move work?" My answer is usually "your core, your arms, your back, your balance, your coordination, your proprioception, etc....." and the looks I get in return are either of confusion or of someone seeing the light.
So I thought, maybe everyone should be asking themselves that question at the gym. And I think the answer for at least 80% of the moves you do should have at least three components to it. If you ask yourself "what does this move work?", and all you can think of are "umm... the calves..?" you're probably wasting your time. (Outside of rehab specific work.)
I'm not saying that the occasional vanity lift is a bad thing, but it should be put in when you happen to have extra time, after you've done the real work. We're all really busy, and the moves that will get you in and out of the gym quickly are also usually the moves that are "functional" and get your heart rate up faster.
Hell, I'll admit it. I do bicep curls once in a blue moon. Just because I think biceps look nice. :)