Microsoft cares, and the Business Software Alliance cares, because one potential impact of the ruling would be that the license agreements which come with basically all proprietary software would be rendered null with respect to their restrictions on copying (the argument that IP protection is exhausted at sale of a seed can easily extend to the idea that it expires at sale of a piece of software).

See SCOTUSblog for more:

http://www.scotusblog.com/2013/02/argument-preview-stakes-ar...