To get a lot of emotional value out of reach, they could get us really attached to it.
Either just by cutscenes, or playing as chief in his younger years, on certain training exercises. The spartans grew up on reach, it is about as close to a home as it will get for them. Now if they really build up how attached the spartans were to the planet, it might help make it that much more devastating when it's lost.
It could be used to sort of explain how chief feels through halo1-3. THrough the game he rarely shows much emotion...he;'s practically a robot. Sure he was always quiet, but what's his motivation? What are his feelings on everything? They're completely ignored in h1-3.
Losing every single one of your friends (the only friends you have) and having your home completely glassed could sort of explain chiefs cold demeanor in 1-3. He's lost everything that's ever mattered to him, everything but earth and cortana.
Anyways, i hope bungie puts a lot of emotional content in the game.