Haha, yea and?
I concur... it's the most popular exercise in the gym. However, most guys look like they DON'T workout even though they are there almost every single day.
At least in the gyms I frequent.... and it is quite a few. I've trained in over 75 gyms so far.
That should tell you something. If everyone is doing something to "supposedly" improve their bodies, yet, none of them look the way you'd like to look..... DON'T do what they are doing.
I currently train most days in one gym. Not one person in the gym trains like me. And there is not one guy I would trade bodies with.
Why shouldn't you do curls?
I should have added context to my post. When you are dieting, there is no point in doing curls. Weight training's main purpose during a diet is to maintain muscle mass. In order to do so, you need to focus on heavy, compound lifts. Why?
These lifts are efficient and effective. The recruit the most amount of muscle in the least amount of time. They allow you to use heavy weights. These are things that send the right neurochemical signaling for muscle maintenance.
Isolation exercises are "okay" when you are bulking. Why? Because you are eating an excess of energy. During these times, your body actually has the capacity to build up above and beyond your current muscle mass. So, "refinement, accessory" moves are "okay" when energy is plentiful.
They are futile when energy is not, though. If anything, IMO, they are detrimental on an opportunity-cost scale.
Basically, you aren't going to be adding any appreciable muscle while dieting, if any at all..... so why do exercises like curls?
Even when I bulk, I rarely focus on arm isolation exercises. No matter what my current "energy-state" is, I am always doing heavy compound work. Heavy compound work trains your arms. Hence the word compound.