The first time I encountered an MMO with a confectioner trade to make muffins that buff people, I was enchanted. It is a simple and slightly silly idea with roots in developers learning what players like.
Hunger, thirst, and other biological functions are not common features in MMOs these days, apart from surprisingly common quests to make you clean up poop. Early RPGs commonly had hunger and sometimes thirst, reflecting the intuitive notion that you will starve to death if you never eat. This meant players needed to acquire food (and sometimes water) and eat regularly or else suffer a hunger debuff that might stack unto death.
Players generally hated that. It was the sort of bookkeeping that most people ignore in pencil and paper roleplaying games, like encumbrance. Yes, there are survival games where finding food is a core mechanic, but most of us are happy to assume it happens in the background. More importantly, players hate debuffs, they hate feeling like something is being taken from them, and they hate being reminded of costs over time.
It feels like a tax on playing the game. You are not just spending time and money to play, you must also spend in-game time and money to play. Some games would helpfully give you a timer counting down your “fed” status. How great is that, every second you stand around town talking to people, you can see yourself approaching starvation and watch that food you just bought wear off?
People generally dislike having things taken from them, even something as trivial as a gradual trickle of imaginary copper pieces. Needing to pay just to avoid losing ground rankles. Players will deeply feel a loss where they do not feel a failure to gain.
Reverse the model: most games switched to a “well fed” buff of some sort. No longer was “fed” a neutral state between “full” and “starving” (or worse, a cap with no “full” from which you could only fall). It became the base state from which you go up. Ignore the fact that the entire game was balanced around the assumption that you would always be well fed, so that the base state is mechanically identical to a debuffed “hungry” state. It is invisible and so it is ignored. (Outside gaming, see all the “free” things that are bundled into the cost of products. They seem free because you pay no additional cost, but you are already paying for them in the initial cost. For example, an insurance company that does not charge you for your first crash, but then the cost of first crashes must already be factored into the base insurance cost. For example, the retail price that no one pays so you can see how you’re getting a great discount; your college tuition is the same, as high as possible then start granting financial aid and scholarships until the students feel like they’re getting a great deal.)
The model develops from there. Why have just “fed” when you can have tiers of food, low-level food for low-level characters and so on, a gold sink tied into your hunger non-debuff. You could even have special and magical food, maybe even an actual buff taking you above the base “well fed” state the game assumes and balances around, although given time the harder content will assume you’re using that too, or else no content is too hard to be overcome with sufficiently powerful muffins.
You can see this model in other game mechanics. World of Warcraft’s rested xp (whatever it is called now) originally had five tiers, +X% xp, +X/2% xp, no buff, -X/2% xp, and -X% xp. Players who hated “-X% xp” to death will keep playing happily without noticing that the xp/level costs were scaled up so that the final “no buff” is the same as the old “-X% xp.”