Presumably the article gives a reason for using this code. Where was it from?
Anyhow, this attribute provides a simple way for people to edit what's on screen—such as you if you are the site owner, or people who want to edit their comments etc. Obviously you have to be careful who has such privileges. The list example above is just an example of how to make content editable. It's not a statement about what you should or shouldn't be able to do with lists in particular.