I'm a bit puzzled by that because we do have to put a reason in the refusal letter. There are reasons tied to the legislation. They may not provide the kind of detail that some applicants would be hoping for. We simply don't have the resources to go into great detail about why an application has been refused.
One of the more common reasons for refusals is that people don't provide us the documentation that we requested. We have very detailed application kits. Surprisingly, people don't give all of that information. Something that we've seen far too commonly is that someone will include a letter from a member of Parliament, and they will think that this letter in and of itself should guarantee them a visa when they don't provide the supporting documents.