While what you say is true, the book publisher would already be covered if the clause merely covered illegal acts. Also, it's not as if the book publisher didn

While what you say is true, the book publisher would already be covered if the clause merely covered illegal acts. Also, it's not as if the book publisher didn't know about Woody Allen's issues before they took the contract. More fundamentally, everything you mention could as well be turned around the other way. What if, after signing the contract, the author decided they didn't like the publisher's reputation, and wanted to terminate the contract and self-publish? I expect the publisher would say something like, "hey, we have a contract! that's an obligation on your part!" If the author wanted an equally vague "morals clause" regarding the publisher, which gave the author an out to cancel the contract whenever they deemed it advisable, the publisher would not agree to such a clause.