Because sending them far away doesn't do the same thing. You really can't make that judgment of you haven't read it.

example: the red wedding has several characters that die.

later you see that because the mormont lady died, mormont's people mourn her and are reluctant to start another war.

because the king in the north died, the crown falls to the next child in line, who is lost. in the vacuum of power, greyjoy loses the king's ancestral grounds to bolton's bastard.

because of that death as well, the king's mother mourns and sends a knight after her daughters to rescue them from what has happened.

also the man behind it keeps the groom in the dungeon, uses him as leverage against the groom's uncle, and shows his twisted loyalties.

there's more from just this one event. if no one had died, it would not have been at all so polarizing.