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 made something like:

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.