Stuff decays because of the natural process of decomposition facilitated by decomposers like bacteria and fungi. These microscopic organisms play a crucial role in breaking down organic matter into simpler components. By feeding on dead matter and breaking it down into smaller pieces, larger organisms further accelerate decay. The increased surface area resulting from their actions creates more opportunities for bacteria and fungi to continue the decomposition process. Ultimately, decay is an essential part of the ecosystem, as it allows for the recycling of nutrients and the regeneration of new life.