I was crunching some numbers about TOS with other fans re: the twelve ships that originally launched during Kirk's era as Captain of the Enterprise for that first five year mission.
It made me really appreciate the TOS crew and the wild frontier era that they managed to survive -- not only survive, but became the staple and measure of success for the Starfleet that took shape after them.
Folks forget that Kirk's crew were one of the few of the original 12 Starships launched that actually returned from their assigned mission with some semblance of crew and ship intact.
A lot of information was gathered and established during that exploratory time -- the reason the TOS crew findings are often mentioned in TNG onward is largely due to them being among the lucky few crew who made it back to share their findings during that time.
This benefited every crew afterward who built upon their findings as they revised based on experiences. Things that happened in that time were addressed in regulation later as a lesson learned.
Regarding the 12 ships:
- The Immunity Syndrome (USS Intrepid)
- The Doomsday Machine (USS Constellation)
- The Tholian Web (USS Defiant).
Considering only 12 flagships were in the OG launch during Kirk's time, that is a solid 1/4 of the ships and crews that never made it back.
But those aren't even the ones that were partially destroyed with casualties, or all of the ships where 100% of the ship and crew did not return. There are more:
- The Excaliber was crippled and lost all hands in The Ultimate Computer, and severe damage was dealt to the Lexington, Potemkin, and Hood.
- The Exeter lost almost all hands in The Omega Glory.
So that's 8 of the 12 ships/crews that were launched circa Kirk's Enterprise 5 year mission that were either entirely destroyed, or severely damaged.
When you consider those odds and how so many extraordinarily capable and well trained crews never made it back, it makes the original series crew all the more remarkable.
Not only did they return with the flagship and crew relatively intact, but they literally became the standard on which Starfleet measured and trained others moving forward.
TLDR: They're kind of a big deal.