Most people have no immediate need for such skills. They generally have developed habits and lifestyles that minimize their exposure to potential threats. They are aware that such threat exist, but rather than train to physically fight such threats, they place their effort into things that affect them on a more regular basis.
For the most part, if an adult follows all of the advice their mother gave them when they were little, they will probably never need to defend themselves against an unarmed attacker. Against an armed assailant, such as a mugger, most people simply give them their wallet and leave unscathed.
Given the general poor quality of many unarmed defenses against guns and knives, and that the good ones are still highly risky, cooperation is generally considered the best course of action.
Regarding those knife and gun defenses, I don't care how good a program is: if you take a lengthy seminar and annual refresher courses and do not drill them regularly, any unarmed defenses against an armed opponent that you learned will be worse than nothing at all.
If your mom knows no knife or gun defenses, she won't try them if confronted with an armed man demanding her pocketbook. If John Doe attends a forty hour SD class and learns knife and gun defenses and is confronted eight months later by a knife or gun wielding man demanding his wallet, he may decide that "I know knife/gun defenses" and try them, and most likely, end up as a practice dummy for the mugger and later, the emergency room doctor... or the coroner.
Daniel
