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:

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.