The most basic function of a checklist is to help you remember. Even experts forget important steps.
Memory fails under pressure, fatigue, or distraction. Checklists reduce errors of omission—the things you simply forget to do.
This applies even to routine tasks you've done hundreds of times. Commercial pilots use preflight checklists on every single flight, despite years of experience.
The value isn't that checklists teach you something new. The value is that they systematically remind you of what you already know.
Don't trust your memory for critical tasks. Write it down. Check it off.
A simple mnemonic checklist prevents costly mistakes that happen not from ignorance, but from forgetting.
References
Scriven, M. (2000). The logic and methodology of checklists.