I'm reminded of the impression I constantly received when I first watched TOS - namely, that the Enterprise type was the biggest and best thing Starfleet had, and moreover, the only real "Starship" design. Sure there were other types of ships, but they were just spaceships, not fancy Starships.
I'm not convinced this was intentional, mind you, as much as a combined result of budget limitations not showing other ship classes, and the effort to make Starships (and by extension, the Captain and crew of said ships) something special. Still, it would be somewhat similar to the Hornblower model which we know was somewhat referenced for TOS.
Still, does anyone know more about the Royal Navy during the time in which Hornblower is set, that we might fight useful in our extrapolation?
It was built around having strong fleets in strategic locations, so the biggest, strongest ships spent most of their time on their stations. The vessels that operated independently and undertook the kind of missions that make for interesting stories were usually the smallest types.