It's not about losing money, it's about stealing. If someone acquires something without paying for it, and those items were intended to be paid for, then that's a serious problem that needs immediate attention. I'm probably the farthest person from any knowledge about how to fix video games, but logically it makes sense that something like the book which doesn't affect gameplay mechanics can be a quick fix, while fixing a problem in a raid might but much more complex since Bungie doesn't want to ruin other aspects of Destiny.