Are enemy weapons and armour up for grabs as loot?

I am running the Starter Set Adventure (Lost Mine of Phelvander), and the majority of enemies have weapons and armour. For example every goblin has a scimitar, a shortbow, and leather armour.

When the PCs defeat them, do they obtain these as items?

I ruled at the time that armour is rendered useless by the fight but weapons can be looted. (And then the first NPC shopkeeper they met swindled them horribly, so that worked out OK). But I would prefer to know what the rules have to say on the subject, and I can’t seem to find an answer.