I know that high level meditation is supposed to have no practical purpose, but that is exactly what is bothering me. What would be the utility of that, from an evolutionary point of view, or from a reinforcement learning point of view (where we divide the world into agents and environment, with goals and rewards).

The spiritual utility, as it is presented in tradition, is related to attaining some sort of freedom and realization, a subjective feeling. But I am thinking (devil's advocate) that all are just patterns of activation in the brain, in other words, just perceptions and emotions. And from a practical point of view, there is nothing useful about it - I am referring only to emptiness, not to mindful attention.