No matter how carefully we eat, we occasionally spill or drop crumbs. While we make every effort to keep the build clean, small bits can find their way into cracks and crevices. Pests looking for food can find these morsels causing them to travel further into the building looking for more. Once in the building, they look for places to live and reproduce causing an infestation.
While we could use chemicals to control pests, we choose to trap and monitor as much as possible. Monitoring rather than spraying, creates a healthier environment for people and artifacts that we are trying to save for future generations.
Along with potentially attracting pests, spills can also penetrate into cases, causing damage to artifacts.