The main reason component or HDMI inputs exist on receivers is that you may have more devices that use them then your tv hookups will allow.
If you hookup all video and sound to your receiver, then you only need one of each cable going from the receiver to your tv. This let's you leave the TV on video, and use the receiver to switch between what you want to watch/listen. For instance, if you have video going to tv and audio going to receiver, you would have to switch the tv channel/input to what you want, then also switch the receiver to the audio you want. With more devices, it get's confusing. The receiver will do the switching for you with one easy press of a button.
Adding a all in one remote gets even better. It will control the receiver switching, and the device you want to listen to you. Thus making 8 possible remotes into 1.
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