Isn't preserving workplace security the job of security personnel?
Security guards do play critical roles when it comes to enforcing security procedures. However, they can only do so much. Threats can strike anytime and can come from anywhere, including from the employees themselves. Relegating security duties to security personnel alone will drastically reduce their effectiveness, especially for companies that house hundreds of people.
A secure company involves the active participation of everyone. All employees should have basic knowledge of what to do in the case of emergencies. They should follow the security protocols imposed by the company. Finally, they should be on the lookout for threats, proactively dealing with anything they find.