Edit: Let me rephrase this and say it better. Correct me if I'm wrong, but these vessels are some of the largest in the game, yes? So these 300 people basically will never have to worry about their ship choice, throughout their entire playing time... (unless they really need one of those carriers or something)
That sounds like a lot easier method of playing the game than having to worry about your ship.
Life Time Insurance has its limitations. There is a cooldown period in between claims and the more frequent you make claims within a specified timeframe, the longer the cooldown period becomes. The insurance does not cover equipment, upgrades, and cargo; only hull is covered. Also each and every ship needs to be maintained, logistically speaking. So that $1,250 corvette will cost pretty penny even in hangar fees and fuel. Owning one and being able to use one at all times at minimum costs are two different things. Chances are these ships will be parked unless there's a need for it to be deployed due to their high running costs.
There are larger ships in the game, such as Bengal Carrier.
EDIT:
This game is not about owning "the most badass ship". Each ship is specialised into something.
A fitting comparison is the Titans of EVE Online. While they are the largest ships in the game, they have limited use and cost much to operate. A chain is only as strong as its weakest link. A Titan is only as good as its support fleet, comprised of smaller ships. The Idris corvettes in SC will need support from much smaller ships, be it as escort or fuel carrier, all of which can be obtained in game.
And many ships are multi-crewed, including the corvettes. So even if you had one, you'd need to muster up players to crew it together effectively. Even if you don't own one, you can crew one, or land on one, or destroy one. Think of it as a "communal" ship, paid by the owner to accommodate the need of many.
Population wise, there are only 300 Idris corvettes sold out of 200,000 registered players so far.