Why do you need to pull the files apart?

Pretty sure its because the programs that re-encode the video/audio only like to deal with their own thing - video or audio files

Also means you can work on both at once.. (seperate files)

Cheers,
Bitey

But I dont need to do that when ripping DVD

And you dont if you are ripping a bluray either.

Ripping is just getting the data off the medium - not actually doing much to it.

If your manipulating either tho, the best way is to demux it, then work on it.

Cheers,
Bitey

You don't have to, you can backup the whole disc with everything intact if you wish.

The main people demux, and remux it is to remove all the extras such as the extra videos, alternative language audio tracks, and things which take up extra space. In doing so this can reduce the size from about 44gb down to say a more manageable 20gb, without altering the original video quality. If you want to go further, you can do what is called transcoding, which starts to reduce the video or audio quality in the aim of shrinking it even further (say to 10gb or less).

When you are doing it to a DVD, it is doing the same thing behind the scenes (usually transcoding to get the size down from dual layer to single layer), it is just doing it within one program so it's not quite as obvious.

Yep,halving the storage space is the main reason,I can fit 60 odd blu ray on one of my 1.5 tb drives (I have 4 )
An added bonuse is not to sit through all that crap at the beginning of a movie which you are forced to watch,main movie is but a mouse click away

+1