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Well, in a roguelike or something, where eventually if you don't use your consumables they expire (because you die, or win), then consumables provide another layer of medium- to long-term strategic planning for the players to think about. Instead of just making sure you use your renewable resources effectively in each encounter, you now can also consider spending consumables per encounter at a sustainable rate, but not too few that you die (and lose all your items).

For some games, consumables are a way to keep players engaged (monetarily-speaking) by letting players buy the same bonus over and over again. Instead of having to keep adding power creep upgrades for your most paying customers to buy (and thus making it so the non-paying players don't even think they have a chance because they're so far behind), you can sell them the same item repeatedly, every time the previous copy they purchased expires.

Consumables can be a way for your player to pass difficulty spikes in your game.

Common game design wisdom is to create a gradually increasing difficulty curve. But when your game is complex and its pacing more driven by narrative than gameplay concerns, then this is easier said than done. So you will often end up with situations which are suddenly far above the difficulty curve.

Imagine your player facing such a challenge at one point of your game and they can not overcome it. They are simply not skilled enough and they don't have the patience to train. This could be the point where the player abandons your game in frustration. Or it could be the point where the player looks through their inventory, consumes every consumable they have which gives them an advantage, passes the challenge and continues with the game.

So consumables are one design element which adds dynamic difficulty to your game. When the player is not challenged enough, they will feel inclined to hoard consumables and in turn make the game more difficult for themselves. When the player feels overwhelmed, they will use their consumables to bring the difficulty down.

It is one of the few ways to create dynamic difficulty which is both under the control of the player (unlike automatically making enemies weaker when the player loses) and plausible within the fiction of the game (unlike a difficulty setting in the game options).

In addition to what Foxwarrior said, consumables are a perfect way to include effects that would break your game if they were available all the time. Imagine you make a game level that is exactly balanced with your player abilities, and then some player gains an unlimited healing capability.
The balance is right out the window, the level will be too easy, you will have to introduce much harder levels afterwards to account for that healing capability. Worse, in a group of players one will be assigned the boring task of a "Healer".

Give the player a single potion of healing he can consume - the balance stays where it is. It's just a nice one time bonus for emergencies.

In some genres (specially MMORPGs), consumables are used as Money Sinks. They prevent inflation and prevent money to become useless once you have acquired everything buyable that's not consumable.

Consumables can be used as a push-your-luck or risk-reward mechanic. Does the player want to use them now? Or is it better to wait until later? in Foxwarrior example the player gets the consumables at a certain rate and don't want to use them any faster, because if they run out, the player could find themselves in a dire situation. That is a risk to be managed.

For another example, we could design the game with stretches where there is no access to some kinds of consumables, usually accompanied with closing the door behind the player. This will lead to three main behaviors:

• The player would have to manage what they got carefully (do not use much more than needed).


• If the player runs out or is running out of the consumable then the player will advance more slowly. This means the player will pay more attention to their situation and ways to get around without the consumable. This gets the player to try alternatives ways to progress and also increases the duration of the game.


• On failure and retry, the player will probably look for ways to stock on large amounts of the consumable. The design could also leverage that to get the players to explore.

Even though it is not what we usually think as a consumable, consider a shooter where the player can run out of bullet (not unheard of). Aside from the behaviors above (preserving bullets, aiming better - or perhap trick shots -, and looking for bullets), it will force the player to try other weapons. That helps ensure that all weapons have a chance to see play. Furthermore, in competitive game-play, trying to make the other player run out of ammo sometimes is a viable strategy.

Consumables add resource management to a game. They allow/require a player to manage limited resources, gather, collect and consume them and plan strategically when and how much to focus on it.

The incentive for the player has been detailed in other answers ("ace up the sleeve", mastering spikes, etc.)

The incentive for the game developer is to add this aspect of resource management and thus more depth to a game and it allows the developer to be a bit more lazy. Instead of ensuring that an encounter can always be mastered by the player, adding some consumables to allow the player to overcome even (slightly) overpowered encounters or solve puzzles that require specific values or abilities (that you can alternatively provide through consumables).

It's called having An Ace Up Your Sleeve. Knowing it's there releases endorphins. Using it probably inhibits your serotonin re-uptake.