More generally, when you are coordinating activity with others.
If the code being deployed requires announcements to users, Help Desk people, changes to other applications, changes do documentation, etc., then these are not "artificial" at all.
If you're truly a member of a "team" (one that includes the positions of Marketing and Sales), hard deadlines are simply a fact that cannot be avoided (unless say, you're Apple Inc).
The key is for everyone to understand the difference between aspirational goals, and deliverable goals for the deadline.
If you're fighting this battle constantly, I'd take that as a sign that you're not a player on the team. Ball boy.