And making Luke think Obi Wan might be schizophrenic.
Originally, Though ...
Surprisingly, like a whole bunch of computerized bulls**t in the special editions, this moment wasn't in the original script. In the early drafts, Alderaan was supposed to be a main setting, the home of a "Sith prison."
Imagine Oz, but all the guards can shoot lightning bolts from their dicks.
The idea was for Luke and Han to go to Alderaan and break Leia out prison, but when Lucas got his budget, it was relatively low for this type of film -- about half the amount of that year's Bond movie, The Spy Who Loved Me (which, to be fair, had to pay the cast double to pretend that a 50-year-old in a tuxedo was a murderous sex machine). So Lucas was forced to cut all the Alderaan scenes and relocate them to the Death Star, meaning the station would have to have a detention level instead of hundreds of gift-wrapping rooms. And since going back and deleting the word "Alderaan" from earlier portions of the script was probably a huge pain in the ass, Lucas reworked the story so Alderaan gets blown up.
This also probably explains one of the movie's biggest problems: Why is Leia comforting Luke over the loss of an old guy he met yesterday when her entire family was the victim of space genocide? Since script-writing software wasn't a thing yet, it would have been harder to delete this scene or add the detail that Leia is fighting back intense rage and sadness while gingerly draping a blanket around poor Luke.