When your subject is brighter than the background,
- it stands out more.
- it has more detail,
- and above all, it has less noise.
Noise, like cockroaches and bedbugs, hides in the darkness.
I could give you engineering, math, signal-to-noise-ratios, and so on (yes, I am an engineer), but just take it from me.
And often, making your subject brighter is easy to do.
Here is a glass on a table, as you can see.
Now again, but this time with a TTL flash from out left, and no flash on the camera:
And as you see, the second one is more dramatic, the glass looks better.
Note that in the second image, I set ambient exposure to minus two stops. In other words, in manual mode, I adjusted ISO, aperture and shutter until the meter read -2. (Alternately I could have used program mode or aperture mode, and adjusted exposure compensation to -2 stops).
Why? Because I do not want the background to be totally dark.
My advice: try this yourself, right now. If it does not work, fiddle around until it does. Or ask me.