Smart drops

Smart drops are where a dropped item (which includes crafted items) has a chance to roll the appropriate item type and mainstat for the class that finds it.

Blizzard have explained why they are random and not guaranteed to be smart drops.

The rationale behind making smart drops a chance rather than a guarantee is two-fold. The primary goals are:

a) give players the opportunity to find off-class drops so that they can share them with other characters on their accounts as well as friends and followers, and

b) improve the overall item hunt, yes, but still maintain the innate randomness that's core to Diablo itemization. If all drops were smart drops, the pool of possible items for your character would narrow significantly.

Instead, we're working to strike a good balance between smart drops and normal drops so that you're not starved for upgrades, but also not overly full of them either.

The drops in this context is an item that is generated for you so that can be loot from a monster or object (chest) or acquired by way of crafting with the Barbarian. A general item would have a chance of smartly crafting as it were a class-appropriate main stat, unless the item can only be worn by a particular class. If, for an example, a Demon Hunter crafted a Mighty Belt (an item only the Barb can wear) it will not roll with a main stat of Dexterity, the main stat of the Demon Hunter or Monk.