Why the left leg is kept in front oftentimes?

You may switch your legs with either of the leg in front, with a light hop and jump as you move around. But that is not so essential. You can continue to keep the left leg in front. There are several technical reasons why this is done.

• It confuses your opponent. Because he anticipates that you will always kick from right if your left leg is in front.
  
• But if you learn to power your left leg with quick, power kicks, you can confuse him by maintaining the same stance and kicking from either of the leg.
  
• The right leg is the more powerful leg, so keeping it behind gives it the scope for a deeper swing and therefore more build-up of power.
  
• Since the left leg is the weaker one, you can use it for quick jabbing kicks more effectively from close quarter. The same logic applies for your guard position with your hands also.