[contrarian1234]

that doesn't really make any sense. You'd just overestimate the time and if you arrived ahead of schedule you'd wait out at sea for the "correct" time

[dvratil]

But that's extra time when the ship is sitting idle, while it could've already been on its way with new cargo, making more money.

[deepsun]

Not so easy. Oftentimes there's no place to store the offloaded containers, and parking spaces are limited too. Probably a ship can also park "on the street" aka in open ocean, if weather agree, but I didn't see that.

Same thing with train carts that arrive to pick up the containers -- there's little place to park them to wait.