I’ll tell you why, because you get 3X the signal carrying capacity. Try this experiment: if your TV has component inputs unplug your RCA jacks and plug them into the component video outputs from your DVD player to your TV inputs. I use Red=Red, White=Blue and Yellow=green. The cables are the same, just colored differently. During this experiment you wont get any audio, but I want you to see the difference. If you don’t notice a substantial improvement in the picture make an appointment at the eye doctor, because you are definitely visually impaired.
This works even with a standard DVD player, and a standard def TV, as long as it has component inputs. Why? If you use RCA your DVD cannot put out any higher resolution than what a VCR can do, perhaps 320i. The DVD can do 480i if it’s standard, 480p if its a progressive scan. Couple that with the superior stability if the digital media storage format and you see why VCR’s are going the way of the dinosaur.
The more modern formats can go as high as 1080i and 1080p, but your TV has to be able to accept 1080p over component cables. Not many do, but the Sharps and the Sony XBRII’s do. HDMI is nice because it can also carry the lossless audio signal in addition to the video, requiring only one cable to the TV.
One last thing, you only need the really expensive component cables if you have a lot of electronic interference. I have achieved superb results with a $4 video cable. Expensive HDMI’s are even sillier, as it is a digital signal, either it’s there or it’s not, quality will be exactly the same as long as the signal is carried.