What draws ants to even the most remote sugar crystals? What entices bees to flowers? It's the fundamental code of life. Hunger is a taste of yearning your life code carries that, when seated into a human body, translates into mental and bodily desires. In the short term, within a single life, childhood limitations or arousals sow the majority of the seeds of desire. Most human goals frequently revolve around good food, good clothing, intimacy, artistic/scientific expression, and financial success. Across multiple lifetimes, it all ties back to our underlying evolutionary hunger. That is why some of our dreams are unexpectedly different from our waking life goals. That is why siblings born from the same parents, nurtured similarly, have weirdly different life goals - they are two different manifestations of two different derivative codes. This multi-life journey, when unaware, is exactly what we attribute to destiny, and when a little aware, we attribute to Karma. Once these little tributaries are done with their own little flow, they flow back to the original river.
In the grand existential scheme, as temporary and evolutionary desires are satisfied, we flow back with the current of existential hunger. This cosmic hunger is more of playfulness than a hunger, simply consciousness, with minimal interference from senses or other impurities, being drawn towards matter, like a playful snake chasing its own tail. Yes, it might be perplexing to our worldly mind. You remember the symbol Ying Yang? The dark dot is the matter in consciousness, and the white dot is the consciousness in Matter - like a lover playfully chasing their loved one. It's a merging of the two fundamental ingredients of existence.
Spirituality strives us to ride the original current, fulfilling and freeing us from temporary desires, allowing us to become one with that primordial life code. That is why a Buddha's desires can be attributed to the desires of existence itself. Life, in its microcosm, is complex enough, let alone the macro one.