Any self-respecting modder will sleeve his wires. It's really that simple. The problem is, it can be one hell of a pain in the ass to do. So when cable sleeving kits come out, a lot of people flock to them in the hopes of saving themselves some grief. Frankly, they are useful not just for power supply units, but also for any other wires you need to run in your box; fans, front panel case wires (power/reset/activity LEDs), etc. The benefits are not just aesthetic, however. Sleeving your cables also allows air to flow better in your case.