The primary function of a load balancer in network architecture is to distribute incoming network traffic across multiple servers, ensuring optimal resource utilization and reliability. By balancing workloads, load balancers prevent any single server from becoming overwhelmed, which enhances performance and availability. They facilitate fault tolerance and redundancy, allowing seamless access to applications even during server failures. By implementing load balancers, organizations can improve service responsiveness, support scalability, and provide a better user experience through efficient resource management and distribution.