Because having 2 free hands for other tasks is better! A headlamp will certainly make anyway easier in the dark easier. Yes, a handheld flashlight is great, but when it comes to cooking in the dark, fire starting, walking in the dark, applying first aid, and a series of other tasks that require both hands, headlamp is the best!
Look for important features such as: Water resistance. Quality & easily adjustable head strap. Type of battery used. Brightness, Lumen rating.