1) They don't want to get into a discussion which is likely to be time consuming. It's not just innocent people who appeal these things, often the most guilty are those who will most actively and vocally profess their innocence (in some cases up to and including going to court over it - c.f. the UK politician Jonathan Atkin).
The minute Amazon became willing to talk about this stuff they'd need a who bunch more people to start looking into each one in detail, review every claim and counter claim and so on, and they clearly don't think that that's a good use of their money.
2) The sorts of things they'd likely have to reveal are going to be the sorts of things people who are abusing the system want to know to get round it. Doing this would make their job harder.
Not saying that it's right that they take this approach, just I can see the reasons they do.
