Why? The Motion Picture footage serves the purpose it was intended to. Remember, the home video era hadn't taken off yet so I doubt anyone actually remembered those shots even being in TMP. And why would you ditch the amazing model work done by ILM?
A lot of it was good FX back when it came out in '82. Now it just looks crappy. Except for the fight in the nebula.
The shuttle docking in the Engineering section when the ship is in 'drydock', but the crew entering the ship in the Photon Torpedo bay.
The Enterprise looking like it already has battle damage in Engineering before the Reliant even fires on it.