We were TOLD Leia was from Alderaan. We'd never been there. We'd never met anyone from there other than Leia. As a matter of fact, we'd only JUST found out she was from Alderaan.
Spock was from Vulcan. As were all the other Vulcans we'd met before. We've been to the planet many times. We knew a lot of it's culture and history. It was destroyed for an easy tug at the emotions.
No, it was destroyed to make a clear statement that this was a new reality where all bets were off. And it was destroyed because tentpole sci-fi movies are required to be blockbusters with high stakes, and because the relaunch of the
Star Trek franchise had to be big to grab the attention of new audiences.
Again, that's the key point that mustn't be overlooked. This film wasn't made just for the established fans, the people who were familiar with Vulcan. This film was made to introduce the
Star Trek universe to new audiences. To this film's target audience, Vulcan was just a name, probably less familiar to many of them than Alderaan. They came to know it only through what they saw onscreen, both of the planet itself and of the reactions of Spock and Sarek to its destruction. It wasn't about what Vulcan meant to the audience, it was about what Vulcan meant to the characters in the story.
In
Star Wars, Leia gives no sign of being upset about Alderaan after her initial reaction to its destruction; the film cares more about Luke's loss of Ben than it does about Leia's loss of her family and whole planet, and at the end of the film Leia is smiling and happy. But ST'09 doesn't shy away from the emotional cost of losing a home planet; it's the single thing that drive everything Nero does, and it's evident in Spock's behavior (both of him) throughout the remainder of the film. It's far less of a trivial plot point because we're shown the cost, because it's not forgotten for a moment that these tragedies happened and are weighing on the characters. And that's much smarter storytelling and characterization.
It required the Vulcans to be oblivious to what was happening above their own planet...
No, it didn't. We saw that the
Narada was able to destroy an armada of six Starfleet vessels without difficulty, and even the
Enterprise, the most powerful Federation starship ever built, was defenseless against it in the initial attack. It's logical to assume that Vulcan's planetary and space defenses were entirely aware of Nero's attack but were neutralized just as easily.
Romulus was destroyed simply to give motivation to a cardboard character.
In both cases, rather than being treated as major parts of Star Trek, both planets were turned into red shirts.
A redshirt is someone whose death is incidental to the plot and the characters -- someone that Kirk spends 20 seconds mourning before moving on to the fighting and the kissing of space babes and the laughing with Spock and Bones at the end of the episode. A death that serves to provide a character's core motivation is more than a redshirt death. Romulus here is the equivalent of Marla McGivers to Khan, or Soran's wife. Vulcan here is the equivalent of, say, Sam and Aurelan Kirk. Using tragedy to motivate a character is a standard storytelling convention that goes all the way back to Gilgamesh and Grendel's mother. Was Hamlet's father a "redshirt"? Were Thomas and Martha Wayne, or Uncle Ben Parker? For that matter, what about the planet Krypton?