It varies from attacker to attacker. Motivation plays a major part in this, thieves look for vulnerable targets who appear as though they may carry a lot of money on them. If they are attacking just for the "fun" of it, it could be for something as simple as the color shirt you are wearing conflicts with their gang colors, to something as deep and complex as their own personal mental psychosis causing them to hate anyone with a moustache or something stupid like that. You can't let fear dictate your life, exercise your right to carry and stay safe.
Perhaps, if I am very lucky, the feeble efforts of my lifetime will someday be noticed, and maybe, in some small way, they will be acknowledged as the greatest works of genius ever created by Man.
- Jack Handey