When users navigate to a file and attempt to open it via Office Online, if they don't already have the Office Online integration added, they are not prompted to manually add it (like a user is prompted to download Box Tools).

Having a direct link to add box for office online so that users can themselves add this app like you see for Installing box tools will save users time, reduce internal IT tickets and requests for the admin to take care of, and allow for easier adoption of the integration by end users.