Because no one really likes cardio...
The need to have an efficient and healthy cardiovascular system is vital to human function. This is a given. Over the years "cardio" training seems to have taken over as the dominant factor in achieving this while weight training is seen as purely for building muscle and strength.
This could not be further from the truth. To achieve an efficient cardiovascular system you need to engage your muscular system which is dependent on the blood and oxygen supply from the heart and lungs. A system that can effectively incorporate both cardiac and muscular work is High Intensity Resistance Training. This does not mean explosive weight lifting or non-stop sprinting and jumping.
HIRT is designed to utilise common weight training exercises and create a high intensity environment for the heart and muscles to adapt to leading to an increase in physical strength and cardiovascular efficiency.