Until 5 minutes ago, I thought the purpose of using Identify would be to detect curses or similar effects that aren’t revealed by spending a short rest experimenting with the item.
However, that’s when I stumbled over the following paragraph in the DMG (p. 138/139, emphasis mine):
Cursed Items:
Some magic items bear curses that bedevil their users, sometimes long after a user has stopped using an item. A magic item’s description specifies whether the item is cursed.
Most methods of identifying items, including the identify spell, fail to reveal such a curse, although lore might hint at it.
A curse should be a surprise to the item’s user when the curse’s effects are revealed.
Attunement to a cursed item can’t be ended voluntarily unless the curse is broken first, such as with the remove curse spell.
So, turns out Identify won’t actually detect curses on magic items (which is also not directly hinted by the description of the spell. Not sure how I came to that misunderstanding).
What’s the purpose of even bothering with Identify, then? Unless your DM disallows identifying items during a short rest (“Variant: More Difficult Identification”, DMG p. 136), I can’t imagine many situations where figuring out an item’s properties would be so urgent that you can’t wait for a short rest – or at least not if curses aren’t even revealed.
Identifying spell effects currently affecting an item/creature or spell origins of an item, learning the number of charges of a magic item, and dramatically reducing the time expense.
You can use the identify spell to identify any spell effects an item or creature is currently being affected by or the spell used to create an item (see the spell description from the SRD or PHB).
You learn whether any spells are affecting the item [you touch throughout the casting] and what they are. If the item was created by a spell, you learn which spell created it.
If you instead touch a creature throughout the casting, you learn what spells, if any, are currently affecting it.
The short rest option for identifying the behavior of magic items does not replicate the options above, since the short rest option only applies to magic items (and, depending on how the rules are interpreted, maybe even only those that require attunement).
In addition, you learn how many charges a magic item has.
If [the item you touch throughout the casting] is a magic item or some other magic-imbued object, you learn its properties and how to use them, whether it requires attunement to use, and how many charges it has, if any.
The short rest option makes no mention of learning the number of charges, although it is common for a DM to rule otherwise (see the description of this activity in the Magic Items, Attunement section of the rules from the SRD or DMG).
[A]t the end of the short rest, the creature gains an intuitive understanding of how to activate any magical properties of the item, including any necessary command words.
Finally, the above advantages are in addition to the reduced expense of time. In order to use the short rest option to learn a magic item’s properties and also become attuned to it, you actually have to spend 1 short rest learning its properties and then another becoming attuned.
Attuning to an item requires a creature to spend a short rest focused on only that item while being in physical contact with it (this can’t be the same short rest used to learn the item’s properties).
That’s a total of 1 hour of resting to learn some of its properties (or 2 hours if you also want to become attuned), as opposed to a 1 minute casting time to learn all of its properties (or 1 hour and 1 minute if you also want to become attuned). Since identify is a ritual, it can also be cast in 11 minutes without expending a spell slot.