According to the provided content, there are several reasons why children cannot do exercise on a regular basis. The major reasons include: (1) Lack of time and energy, (2) Negative effects of parents pushing their children into playing sports, (3) Fear of getting hurt or injured, (4) Lack of encouragement and support from family members, (5) Limited access to safe and suitable places for exercise. Additionally, it highlights the importance of exercise for children's overall health and well-being, citing benefits such as improved physical fitness, increased self-esteem, and enhanced cognitive function.