Self defense can range from a few simple moves to try and dissuade an attacker to more complex techniques that not only ward off the attack but turn the tables on the situation. For many these complex moves are a little more than they wish to learn since they only want to not be the victim of a crime. This is often for the best since the complex moves can be harder to perform should the student ever be under duress from being under attack.
Simple self defense moves are all most people need to thwart an attack and prevent themselves from becoming the victim of a crime. From stopping a robbery to a rape most attackers will choose to retreat instead of fight making complex martial arts self defense unnecessary. While complex moves can turn the tide and turn anyone, even smaller women, into the aggressor they are not as easy to implement.
Using simple moves to fight back will not break the arm of the attacker but they can be practiced so they are automatic even under stressful situations. Using elbows and knees as weapons can do a significant amount of damage to an attacker without doing any to the victim swinging them. It is almost instinctual for many to start swinging and kicking when under attack so this type of martial arts training is easy to learn and effective as well.
While some want to learn the complex moves that turn them from victim to attacker in order to make anyone pay who is willing to mess with them. Others simply want to know they can prevent an attack on themselves to avoid being a hurt by someone who has ill intentions for them.