The prefrontal cortex manages 'Working Memory'—the scratchpad that holds active tasks. It also manages 'Time Perception.' When both of these are impaired (as in ADHD), 'Maintenance Chores' become mathematically impossible to sustain via willpower.
A neurotypical brain can maintain a low-level background process: "I fed the dog 8 hours ago, so it's time to feed him again." The ADHD brain deletes background processes to conserve energy. If the dog is not actively barking in your face, the concept of the dog's hunger simply does not boot up in the brain.
Furthermore, cleaning a litter box is a "High Friction, High Disgust" task. The ADHD sensory gating system is highly reactive to bad smells and unpleasant textures. The amygdala actively discourages you from approaching the litter box, creating an invisible forcefield of avoidance that you must fight against, leading to infinite procrastination.
