Disciplining children by restricting their activities and grounding is important because it directly affects a child's life, and some parents do no see the importance of discipline when children are in emerging stages of their lives.
Children need to understand the appropriate behavior for any setting
When a child understands that they will be able to build on top of the understanding of consequences and authority.
This will directly affect the child’s life and behavior as they grow up in any setting.
When a child acts out repeatedly in school for example, they are isolating themselves from the rest of their classmates. The other children see them as uncooperative and difficult, and they distance themselves away from that.
Discipline plays a big role on how children view respect for authority and consequences, and by learning appropriate behavior children can succeed in that.