Human nature is defined by a constant, restless desire that never seems to be satisfied. This deep psychological state mirrors the endless reality of death and the grave. The concepts of the underworld and destruction represent the burial pit, hell, or the total loss of existence [מצודת ציון, מצודת דוד, עמנואל הרומי]. The primary approach among commentators is that just as the grave and hell endlessly swallow people without ever becoming full, human eyes are never satisfied with worldly possessions and the drive to gather more wealth.
The focus is placed on the eyes because they act as the gateway for worldly temptations, passing these sights down to the heart, which then forms a craving [עמנואל הרומי]. This endless cycle of greed acts as a kind of internal hell that a person carries within themselves [ביאור שטיינזלץ].
Beyond a simple comparison, this reality carries a strong moral warning. Just as the underworld never tires of taking in the wicked, a person's eyes never tire of chasing the evil inclination and trying to fulfill every desire [רש״י]. There is also a tragic irony in what people choose to observe. People constantly see others dying and descending into the endless grave. Yet, instead of taking this reality to heart, correcting their behavior, and avoiding sin, they simply ignore what is right in front of them and continue chasing their physical cravings [אלשיך].
On a deeper level, this lack of satisfaction is tied to the physical and philosophical makeup of the world. The basic matter that creates humans and the universe is in a constant state of change, losing one form to take on another. Because of this constant shift, matter is always lacking something and requires renewal. As a result, it is human nature to always seek out the new; the moment one physical desire is fulfilled, it fades away, and a person immediately looks for the next [מלבי״ם, רלב״ג]. The persistent search of the eyes for new sights and experiences perfectly matches the concepts of emptiness and destruction found in the underworld [אמרי דעת].
Interestingly, this insatiable drive is not limited to physical goods or wealth. It also applies to the human mind, which is never completely satisfied with its current understanding and is always hungry for new knowledge and wisdom [רלב״ג].