I can't be totally sure, but I would assume that it has lot's to do with broadcasting rights. Although many of us are watching everyday on our computers for free via SopCast, the video is a product of ESPN Sports, and they probably have exclusive rights to the coverage. I don't know if you've been watching or not, but SopCast has been wonderful this year. Probably the best quality and consistent live coverage I've ever seen when it comes to watching a major even live with my computer. In the past I've subscribed to BCN coverage of the US Open, but this SopCast quality and consistency is running circles around any of the BCN programs I've watched.
dave