Why when something goes by car it's a shipment and by boat it is called cargo?

Answer 1

Sometimes it's freight, sometimes it's Carthage... the terms are interchangeable, no laws dictating what mode of transport for which term is to be used...

Answer 2

*Cargo comes from the latin words carricare and carcare meaning "to load" not from the modern machinery we call car.
*Shipment comes from the word schiff, which is germainic in origin. Shipment, and specifically, to ship, usually meant to be sent on a vessel or ship.

Along the same lines, why do you park on a driveway and drive on a parkway?

Answer 3

so people know the difference between car and boat travel