Publishers and agents hate it when authors share the specifics of our contracts with each other and that is precisely why we can, and must, share all the details of our deals.
Publishers don’t want authors sharing information — sometimes so much so that it is written into the contract that the terms and conditions cannot be shared — because publishers feel they need to preserve a hierarchy among authors. They don’t want one author knowing another, perhaps “less talented” author, was able to get a better deal because then all authors will want the same deal and that costs them money.
Agents don’t want authors comparing notes for the same reason: Every author thinks they are the best and that they alone should get the highest deal and contract terms. When authors share information, all heck breaks loose, and the world of the Author/Agent relationship begins to sour when authors share their contract terms with each other.
Keeping authors in the dark is what keeps other authors down because to be able to say to a publisher and an agent that you want the same deal the other person has evens the playing field for all authors because no one wants a lesser deal than what they already have — and that is a dangerous notion in the marketplace of ideas — but in the end, the only thing the author owns of true value is the unique expression of the idea in text and images and none of that magic should be kindly, or implicitly, relinquished to the lowest, common, bidder.