It's necessary because having a clean work area ensures that dust and other particles may not cause any damage to the computer or electronic parts and hardwares before starting any repair, assembly or disassembly. It's also necessary for safety purposes.
Especially when it comes to repairing Hard Disk Drives (HDD), the work area should be clean and dust-free so that when opening the hard disks, it won't get damaged from the particles that makes data recovery harder.
