Why do some U.S. airports have private security, but others use TSA?

At Kansas City International Airport, the officers checking IDs and screening luggage are not TSA employees but private contractors from VMD Corp. Despite wearing badges and U.S. flag patches, many passengers don’t realize these officers are not federal employees. This setup is part of the Screening Partnership Program, allowing airports to choose between federal and private security. VMD Corp. ensures they meet TSA standards, with TSA teams auditing their procedures. This approach stems from post-9/11 security changes, offering airports flexibility in managing security while maintaining safety standards. QUESTION: How might the use of private security contractors at airports influence passengers’ perceptions of safety and efficiency?