Final answer:
Restricted areas are confined because of their national security significance, often established to limit entry and usage for safety and strategic reasons.
Step-by-step explanation:
Activities within restricted areas must be confined because of their national security significance. Such areas are established to limit entry, extraction, and use of a designated area, often due to the presence of sensitive operations or materials critical to a nation's security. Restrictions on land usage can be due to various factors, including environmental protections, zoning regulations, or national security, as with the case for restricted airspaces where both commercial and military aircraft operation is carefully regulated for safety and strategic reasons.