Just thought of this the other day. Came to the conclusion that they think you already dropped $xxxx on the game so why take the time to explain to you the rules? It's not going to help them sale any more games (even though I think it may), and it just costs them more time and money.
I haven't looked but is there a website that allows users to upload rules for games? I think it would be beneficial. I could tell you the ruleset for rollergames, sf2, hardbody, and playboy backwards and forwards. Would be happy to share the knowledge, just don't know where the best place would be...
Maybe it is something that could be done here on pinside? Is there an interest by others to start putting rulesets up?