Torrents are great, but most people don't know what they are and won't want to download a torrent client just to get the supplementary materials for a textbook. Using Akamai, or other similar services, means they'll just have to stick their code in and click a link.
That would cost a lot though. With torrents you have the chance to save some bucks (at least on bandwidth costs, the deployment/coding might be much more expensive).
Torrents are great, but most people don't know what they are and won't want to download a torrent client just to get the supplementary materials for a textbook. Using Akamai, or other similar services, means they'll just have to stick their code in and click a link.