The Batman’s Character is dark which the result of a childhood trauma of seeing your parents murdered right in front of you. A very Dark, brooding character that instills fear in his enemies that aids him in his fight against crime.
Although his persona as Bruce Wayne, is a completely different from his Batman persona being a millionaire playboy an eternal bachelor as told by Selina Kyle. As stated, in the comics that whenever he dons the Batman costume, he changes into his dark, sinister side that his enemies cringe at the sight of him. The purpose of his Dark costume, is to be able to hide himself in the shadows.