wav to auto open with VLC Media Player, you are saving your self some time and trouble.
You would do this to remove associations from other players such as Windows Media Player, for example. To make VLC Media Player your default media software, you will have to change file associations. This would waste a few seconds of your previous time, everytime you have to open a media file.
You do not always want to right click on a file, click on open with and then select VLC Media Player to open with it. When you double click on a media file, you want the file to open with VLC Media Player naturally. If VLC Media Player is your favorite media playing software, you would want a lot if not all of media files to auto open with VLC Media Player.