Where the money goes is all publically available, yes. But it can be split up and fed through any number of accounts (you can make as many accounts as you like) to try to launder it. Also, does Silk Road care where the bitcoin being used to buy drugs came from?
I believe Silk Road is operated by actual agorist, or market anarchists to be more general. If that is true, even they would care about where the money comes from, especially if it is stolen money.
