The element of surprise gives a massive advantage to any individual who holds it. It is an important strategy in Sun Tzu’s art of warfare, and is a strategy that actually comes from instinct. After all, when hunting for food, you want your prey to be caught unaware as it can be the difference between coming home empty handed or coming back with meat.
In combat, striking fierce and quickly can leave the opponent stumbling and wondering what just happened. By that time, it would usually be already too late. In modern days for the brawl, this type of tactic is very looked down upon, but some people just like to win.