Cable management is essential for a data center where multiple sets of maintenance hands, multiple owners, SLAs, fire codes, and cooling/venting needs demand organized layouts.
Cable management is also important for tight spaces (inside walls) and extremely low-duty-cycle, but mission-critical wiring such as a home's breaker-box.
Is it necessary for the typical modern desktop with a few AC Power, networking, and USB cords?
Um, NO.