Couriers are Void Ships specialized for quick delivery of messages, small cargo, and passengers. They are the equivalent of the old “pony express”, physically relaying their cargo from sender to recipient.
Couriers are built for speed and quick pick-up and drop-off of specific packages. Most are small and maneuverable for quick maneuvering into and out of station docks with a minimum of fuss and paperwork. Most couriers are also civilian ships, although there are military couriers. All of this imposes practical limitations on weaponry, so couriers are more likely to flee than engage in combat.
Internets are not connected
“Internets” only exist within systems, not between them. Systems are separated by vast chasms of light years that make real-space communications such as radio unfeasible for timely delivery. What is the point of sending a message that will arrive a lifetime in the future?