Why do they do this?
«But to fill the ship», they will reply.
«And why can't you fill the ship alone?» I ask, «or together with your alliance partners?»
«Because it is too big», they will say.
«And why is it so big?» I insist.
«But in order to enjoy economies of scale», they immediately retort.
«But to enjoy economies of scale», I continue, «you first must fill the ship, while you know you can't. Are you therefore building megaships as a gift to your competitor?»
In my “Gigantism in container shipping, ports and global logistics” (link below), I have proposed a pricing strategy for liner companies, leveraging on their comparative advantage, which is the ‘ship’. In short, 'charge more for the component of the supply chain where you have the comparative advantage, and less for the one where you must compete'. The overall price of the 'door-to-door' transport should remain the same. But the 3PL will have to pay more now for your ship, and this will give you the competitive edge you seek to enter 'logistics'.
Some carriers have listened; especially those controlling marine terminals. Others have not.