The reasons aren't good. If the DAS posted elsewhere in this thread is accurate then they don't want to be seen as "shaming" people, but the behavior they detected is simple promise breaking. The researchers stated they'd share their data, benefited from the aura of respectability that claim created, and later refused. And this behaviour was absolutely widespread: more than 90% of the papers selected didn't provide data as promised.

That's the sort of behaviour that actually should be shamed, right? Why shouldn't people know whose word can be trusted and whose shouldn't? It's a very silly form of ethics that defends the honor of those who deliberately lie for profit. It also totally devalues the efforts and integrity of the tiny minority who did do things by the book.

The actual reason they refused to share their own data almost certainly has nothing to do with ethics. It's because they don't want to make 3500+ enemies within their field.