Kangaroos' grooming and scratching behaviors are very common in young kangaroos and adult kangaroos, but they are all very common behaviors. Looking at them from the front, you will feel normal.
Why can't kangaroos retreat;
Kangaroos really can only jump forward.
Judging from the physiological structure of kangaroo, its forelimbs are shorter, its hind limbs are longer and its tail is stronger. When jumping forward, the tail and the shift of the body's center of gravity can keep balance with the tail and can jump far.
If it jumps backward, the balance between its center of gravity movement and its tail will become very small. If you jump at this time, it's easy to fall.