Because for the user experience, it is identical to <ul>. Use <menu> if it helps you to understand your code but in the browser's accessibility tree and in all other respects, it's just an unordered list.
Conveying that something is a list of actions requires adding ARIA attributes. The article mentions `role=menu` but that's not enough, each item also needs the `menuitem` role. The WAI Authoring Practices Guide explains the roles and interaction expectations; don't copy their coded examples and definitely don't use the roles for navigation menus.