Boxing is a very popular sport that seemed to see its height in the 1980s and 90s. Though the sport is dangerous and can lead to many health problems at the professional level, it is very good for normal exercise. This is especially true when done with a sparing partner.
The sport is great for cardiac exercise and it can also be a good way to vent steam and loosen up tight muscles. This is why boxing can be a healthy activity when outside of a professional fighting setting. Many people in Japan go to boxing gyms for these purposes. It can also give confidence and the feeling like you can really conquer the day.