Okay, I've been playing Reach since it came out, still am, and still think it's great, but Commendations annoy me. What do they do? I've been wondering for a while. Do they boost your amount of Credits earned? If so, I can see why they're so hard, but if not, what's the point? If to make people play more, it'll probably just turn more away. Can someone please explain to me once and for all why I'm so addicted to upgrading them now? Thanks.
(I didn't just ask here straight away, I did Google the query but found no results)