Why did Lucretius think that all material systems eventually perish?

In his philosophical poem De rerum natura (On the Nature of Things), the Latin poet Lucretius explains that all material systems are ultimately composed of moving atoms separated by intervals of void.

Because these systems are constructed from these moving parts, they are inherently divisible. Lucretius posited that all such systems are therefore perishable, as their existence depends on the specific arrangement of atoms that can be altered through the addition, subtraction, or rearrangement of those particles. While the atoms themselves are changeless, everlasting, and the limit of physical division, the composite structures they form are temporary and subject to dissolution.1