Accidental deletion of uninstalled programs on Windows can happen due to various reasons. Some common reasons are: - Forgetting the importance of the program and uninstalling it. - Human error, such as accidentally clicking on "delete" instead of "cancel." - Software monitoring that automatically uninstalls programs that are not frequently used. - Malware or viruses infected the computer and deleted important programs and files without the user's knowledge. - Issues during the repairing process of an app that led to accidental removal.