Tug boats don’t usually tug. They push.
That’s because pushing is more mechanically efficient than pulling. When we pull, there’s tension and slack in the ropes, and the attachment between the puller and the pushed keeps changing.
But the metaphor gets far more interesting when we think about leading instead.
One bird at the head of the flock can lead 100 others if they’re enrolled in the journey. That bird would never be able to pull (or push) even one bird, never mind all of them.