Samara dying during the Long Walk just seems wrong. When I picture that, I can just imagine Shepard going "Okay, maybe I should have had her
do the biotic field..."
Well, my rationale is that I bring her alongside Jack for lots of biotic goodness through the swarms. I sort of headcanon the idea that she'd be the backup in an emergency, but since Jack makes it all the way across, she instead flings Reave all over the place and then gets taken down at the tail end.
I dunno why I like it, I just do.