Because efficiency is the name of the game. If you miss your slot time in a busy port you might spend some days or a week waiting on the next and now you have c

Because efficiency is the name of the game. If you miss your slot time in a busy port you might spend some days or a week waiting on the next and now you have cascading logistics issues, both for the ship in question and the cargo getting sorted and sent forward. The real issue is stowage, sailing for example north Atlantic in the winter you need to expect bad weather but there seems to be a missmatch between the regular lashings and large stacks right up to the stack limit by weight wee see today. There's also designs like this [0] but that's more expensive to build and they lose 1-2 rows of containers. [0]: https://en.m.wikipedia.org/wiki/G4-class_freighter https://en.m.wikipedia.org/wiki/G4-class_freighter