A file with the matter, not in an attachment from half a year ago
An attachment added to a task stays with the task - together with the comment it came in and the person who uploaded it. The company drive holds what does not belong to a single matter: contracts, templates, brand materials. Both have the same access control as the rest of the system.
Sharing without sending copies
A file is shared with a link that can be protected with a password and revoked. The server delivers user files in a mode that blocks anything from running in the browser - a technical detail, but it decides whether a file someone uploaded can do harm.