Low kicks are excellent tools in any self defense arsenal. I started learning Tae Kwon Do which only allows kicks above the waste. When I started MMA and Sanshou through my Kung Fu school I learned the power and versatility of low kicks. They are really effective against larger opponents. Opponents with weapons and you can use them in close quarters. It also takes the steam out of bigger and powerful attackers. If you meet a power punch or fast punch, kick their legs. power and speed come from the legs. Get those out of the equation and you have leveled the playing field.