I can easily spin that around on you. People who would rather download the disc are going to find a way to download it, if they have no way of paying for a direct download theyll torrent it for free.
Have we not learned anything from music and games? The RIAA thought downloadable music would cause more piracy, they fought against the need for a download service despite the popularity of downloading MP3's. They were so wrong that their resistance to digital distribution can be seen as one of the biggest corporate blunders ever. Valve wanted to offer a downloading service for a number of PC games to combat piracy by trying to make the convenience of downloading from a fast server worth the cost instead of torrenting it slowly. Steam became a huge success and stopped a lot of piracy which was beginning to get out of control for PC games.
History proves that offering downloads combats piracy, it doesnt increase it. The more reasons companies give people to download something illegally will only result in more people downloading things illegally.