Why are attackers at stronger positions than the victims?

Today, another terrorist attack hit London tube system again. There have already been several terrorist attacks around the world. People do not only face the threat from terrorism, but also face threat from serious crimes (robbery, murder). Usually we often find victims are always dominated by the attackers or terrorists.

Of course, criminals and terrorists often choose their targets carefully in order to ensure they have the power to dominate their targets. However, in some events where the two sides seem to have similar strengthen or power, the attackers still seem to dominate the victims. This is because the two sides have different preferences thus choosing different strategies.

When a person notices that he(she) is about to be attacked, his(her) preference makes him(her) perfect being unhurt over defeating the attacker. As the priority of the potential victim is to stay unhurt, this individual tends to escape rather than to attack back. The probability of getting hurt is much higher when attacking back than the probability when trying to escape, as getting in physical contact is more likely to be hurt even when the strengths of both sides are similar. Especially when the number of potential attackers is significantly larger than the number of attackers, the probability of getting hurt when choosing to escape is fairly small. Moreover, in modern eras, the information asymmetry also plays a significant role when potential victims are making their emergent decisions. The possible weapons that the attackers hold are more various than decades ago, to the attackers, the information about the victims is almost completely obvious and transparent; therefore, it is much less risky for attackers to attack victims than for victims to face attackers, due to the information asymmetry between the two groups.

Therefore, when facing criminals or terrorists, potential victims automatically become the dominated and vulnerable group that even giving them any sort of training or education is not going to change such position.