Why don’t we have a convergence to immediately available video-on-demand? Edward Jay Epstein blames Wal-Mart:
What has prevented the studios from closing the video window is simple: Wal-Mart. The company, which is the single biggest seller of DVDs, has made it clear that it does not want to compete with home delivery. Wal-Mart executives told Viacom’s home entertainment division in no uncertain terms that if any studio does away with the 45-day video window for a single title, they would risk losing access to Wal-Mart’s shelf space for all of its titles. Wal-Mart provided studios with more than one-third of their U.S. DVD revenue in 2004. In the face of Wal-Mart’s retail power, the studios have not dared (yet) to do away with the protective video window.
Read: Wal-Mart will lose this battle sooner or later. Here is the full article, which contains much more about Cuban.