Does the craft weapon/craft armour skill do anything for you except to make a mundane (non-magical) weapon/suit of armour?

Is it worthwhile taking ranks in these skills?

The Craft skills let you make weapons/armor/traps from basic components, and they also allow you to change the appearance of existing items. Craft Trap might have a use if you rely on traps a lot, the others don't have a place at all in powerbuilds. They are fun little extra's in roleplay settings though, and no tailor/smith character should be without.