The ship we've followed throughout most of Star Trek is the USS Enterprise that maintains the registry number NCC-1701 with a suffix change indicating linage.
Does anyone have a really good explanation why other federation ships that have known long lineages don't follow this registry format?
I can, to a degree, make sense of registry changes when the ship becomes an entirely different class. To that end I can understand rationalize why the Constitution Defiant is NCC-1764 while the most recent Defiant of the Defiant Class is NCC-74205. However, in my mind it makes less sense when a ship name jumps classes. To me it seems logical that once the name Defiant is established as a Heavy Cruiser, the name would always be recycled for use of another heavy cruiser (unless perhaps, heavy cruisers are completely moth balled).
Can anyone give a better in universe explanation better then "They REEEEALLY liked the name and wanted to feature a ship with that name" ?
The Enterprise is supposed to be the pride of Starfleet. Therefore it keeps the registry for purely symbolic reasons, in honour of Starfleet's greatest ship. Other starships just don't have the same impact which is why their registries aren't recycled.
Although, the original plan on DS9 when the USS Sao Paulo was renamed Defiant was that its registry was going to be NCC-74205-A. However, all footage of the ship was stock footage of the previous Defiant, resulting in the new ship also having the NX-74205 registry (which it still has in novel continuity).
Voyager seemed to imply that it was actually a Starfleet ship named the USS Dauntless that had the registry NX-01, since the fake ship named Dauntless had the registry NX-01-A and no one questioned that.
Also, the USS Relativity's registry is NCV-474439-G. The dedication plaque confirms that there were previous ships named Relativity, and presumably the registry is passed down as well. Unfortunately, the plaque states this Relativity is the seventh ship to bear the name, when it should be the eighth. If it really were the seventh, than that would mean the original USS Relativity was NCV-474439-A as opposed to NCV-474439, which it should be.