Nob Akimoto wrote:
in the age of sail warships could often charge freight money
An interesting possibility that Starfleet might charge freight costs for carrying civilian shipping into places where private ships don't operate, or operate rarely.
Like in Dagger of the Mind, cargo going to and from the Tantalus colony.
Add to the list of freighter the Astral Queen. Passager ships do carry freight, and freighters occasional carry passagers.