The exercises in the video are to help promote activation of the gluteal muscle group, these are to help movement of the hips in extension and rotation. The exercises also challenge the core, rotation and mobility for the first exercise, anti-rotation and anti-lateral flexion for the second. All these qualities trained in these exercises are also a key link in an effective kinetic chain, read more here.
If these types of movements are not trained, an athlete can start to super-compensate using other muscle groups, like their back or knee joints. Combine this with high training volumes, intense movements and a low calorie diet, a boxer can be susceptible to injury.