Sometimes for me, natural light works for me, other times it doesn't. Every now and then I find that the subject is darker than I would like. I have a tendency to not want to modify my images after I've taken them. Call me stubborn. So I employ my flash.
Employing my flash brings the subject to the forefront in a rather abrupt fashion. Then you can see the subject clearly and still see the background as well.
I like the results it creates like this pic I've previously posted where the leaf to the left is brought to the forefront while we still see the rest of the scene.
In this case below, if I had not used the flash the leaf would not even show up except as dark shadowed highlight: