Quite true, my mistake.
A pattern is clear there, though. Scuttling is done when there is a good chance it will take the enemy with you, or when it's clear that the enemy is on the verge of taking control of the ship. Unfortunately, we never see a situation where a ship would need to be abandoned in an emergency but wasn't about to explode on her own immediately afterward; if that ever happened, we'd learn if Starfleet really wants to blow up its own starships.
Nobody ever comes out and says that Starfleet is in the habit of scuttling its ships. Scuttling is a valid combat maneuver at times, but Starfleet does other things besides combat. And Starfleet knows how to keep its starships from being misappropriated by people who might want to learn their secrets: explosions aren't necessary for achieving that.
Certainly there'd seldom be a need to scuttle a ship in a non-combat situation, because bad guys (or well-meaning innocents) don't just stumble on derelicts. Nobody salvaged/stole the Stargazer in the intervening decades, not even the Ferengi, before DaiMon Bok with his very specific agenda and knowledge of the Battle of Maxia arrived to claim what he already suspected would be there. The Exeter of "Omega Glory" wasn't salvaged/stolen, either, despite orbiting a planet that might have interested other visitors, and apparently not being completely shut down.
(Granted, the Pakleds managed to salvage Lore, a tiny object compared to a starship. But ST:NEM comes to the rescue here, establishing that "positronic signals" attract attention across interstellar distances...)
Timo Saloniemi
