If I were in Chief's shoes, I'd totally keep that armor. Sentimental value! That ***has been through thick and thin with him! Also, a shot in the dark, but he could be the way he is, due to depression and wearing it as a sign to remember. /wink
But chief has never been one for sentimental value, even if that is the armor that:
he was wearing last time he had cortana before she kicked the bucket
either way, after a lifetime of military service, he would sooner take the new hardware and weaponry at hand than keep old outdated stuff for "sentimental" reasons. Just saying. That and :
final shot of halo 4 was of him getting his armor taken off. you would think that they could at least repair the armor.