Well, energy drinks aren't supposed to make your hyper and all over the place, but rather... energized and concentrated... I mean, it's mostly students and managers who drink them, when needing to study or work on project... So it is logical it helps with the concentration somehow. Though I think the motivation is rather a placebo effect. "I need to finish this and energy drink/coffee is going to help me".

I am not doctor, but I suspect that caffeine has been around very long, so it's tried... Nowadays it's unnecesarily demonized. It is not the ultimate evil and unless you overdose on it, or have health problems like high blood presure, it will probably not cause serious harm.