Player can trivially jettison their cargo, drop their backpack/bag, or similar. Usually to help move faster or gain increased maneuverability when such is needed immediately.
Alternate name: Emergency dumping
The first video game about Cargo jettisoning was released on May 1, 2003.
The emphasis here is on the triviality of the action. Needing to enter inventory screen and drag all items individually off is quite far from what this is for.