Why does the FAA warn pilots against penetrating an active restricted area without clearance?

Why: Remote Pilot Study Guide (pp. 7-8): restricted areas contain airspace within which hazardous activities are confined, and "[p]enetration of restricted areas without authorization... may be hazardous to the aircraft."

• Invents an airline-traffic purpose; restricted areas are established for hazardous activities such as military ordnance use, not to give commercial air carriers priority.
• Overgeneralizes a local airspace restriction into a nationwide grounding; a restricted area's hazard and permission requirement apply only within its own charted boundaries.