Reality does not necessarily need to have a purpose or utility, to be valid. This is not about the practicality of the Uncarved Block, or our true nature, but about its inherent virtue. When we are in touch with that inner virtue, it allows us to see things as they actually are, rather than how our conditioned (ie; 'carved') minds tell us they are. It is our socialized self that is the repository of external authority and its dictates. This is the mind you refer to as one which names and labels reality via learning. The Uncarved Block is the state of mind in which learning, naming, and labeling have not yet occurred, and so it is the original state of our mind, which is that which sees things as they are. What could be more useful than that, unless, of course, you wish to see things as they are not.
No one is saying not to label. The problem is that, through repeated labeling, we mistake the label for reality. That is why it is crucial to keep original nature alive and attentive, so that we can know the difference. Otherwise, we eat the menu instead of the meal. We end up living an imitation of life, wherein life has passed us by before we know it.
Nurturing desire is to live via the appetites, rather than via the intellect. There are three goals of desire, namely Power, Sensation, and Security. These soon become Addictions, requiring greater and greater amounts of them to 'satisfy', but alas, they fail to satisfy in the end, as they are mostly empty calories. They are merely temporal gratifications that feed the ego. Your description of absorbing another's Quickening is a good example of this delusive path of ego gratification, though you may assign some imaginary noble or heroic attribute to the act.
But by all means, give your desires free reign. It is one way of eventually finding out that they lead nowhere. But that is just how good the illusion they create that they are superior pursuits actualy is.