Inspired by What is the lore-based reason that the Spectator has the Create Food and Water trait, instead of simply not requiring food and water?

The Spectator has the Create Food and Water action (Monster Manual, p. 31):

Create Food and Water. The spectator magically creates enough food and water to sustain itself for 24 hours.

I don't understand why the Spectator must to use an action in order to create its own food and water to sustain itself.

Wouldn't be easier to add something like the banshee's Undead Nature trait?

Undead Nature. A banshee doesn't require air, food, drink, or sleep.

They could have given it a trait like this instead:

Spectator Nature. A spectator doesn't require food or drink.

Is there any important mechanical difference between both abilities? I mean, any exploit, advantage or drawback that has create food and water over it doesn't need food nor water.

Generally speaking, the Spectator's ability is far superior.

The Spectator can create food for other people

A Spectator can create a day's worth of food and water every six seconds. A Banshee can't do that, it just doesn't need to eat. A Spectator could use that ability to keep pets or companions, function as the food source for a moderately sized army (a spectator can feed 4800 people with 8 hours of work), or cut down on overhead costs for its food stall.

The Spectator can use food and drink for purposes other than eating or drinking

A Spectator can drown an enemy that can neither swim nor escape a pit with water, or enable an ally to cross a pit with water or food or both. A Spectator can block up a door or passageway with a wall of food. A Spectator can make little statuettes out of food and then play with them. A Spectator can use food or water or both to trigger or bypass weight sensors such as pressure plates. A spectator can create a pile of food which then rots and attracts Otyughs and repels humanoids. A Spectator can create a basket of bone-in wings and then have a pixie minion use one as an improvised club. If imprisioned in a cave with a friendly wizard stripped of their stuff, the Spectator can provide the missing component for the spell Flesh to Stone (It's water. Lime and dirt are usually omnipresent in a cave).

The Spectator can starve to death; its ability can be disabled

If the Spectator wants to take its own life and has no other means of doing so, it can dehydrate to death and/or starve. This can backfire, though, as other creatures can potentially kill a Spectator by starving it to death or preventing it from drinking enough water, for example by placing it in an Antimagic Field.