You're running three marketing departments on one budget
Donors need to believe their money did something. The people you serve need to find you and trust you. The board needs to see that the organization is growing. Three audiences, three completely different messages, one person doing all of it between everything else.
So the one thing that gets resourced is the event, because the event has a date. And the event eats four months of staff time, clears somewhere near its own cost, and the follow-up — the part where a first-time attendee becomes a recurring donor — happens in a thank-you email two weeks later, if at all.
Next year it runs again, because it’s what you do, and the question nobody asks is what it actually returned.