Why can't a CPU access data directly from the hard-drive?

A CPU cannot access data directly from the hard drive because of differences in speed and architecture. The CPU operates at much higher speeds than hard drives, which results in inefficiencies if they were directly connected. Instead, data must first be loaded into the system's RAM (Random Access Memory), which acts as an intermediary, allowing the CPU to access and process data more quickly. This hierarchical structure optimizes performance and ensures smooth operation of the system.