There are lots of reasons why beginner photographer might avoid using strobe lighting, but a common answer is that they don't like the look. While I know exactly what they mean, there doesn't have to be a "look" at all.
Like many photographers, when I was first starting out, I liked the natural light look. I didn't go as far as to call myself a "natural light photographer" — god forbid — but I definitely didn't like how flash made images look. What I felt strengthened my case was that I had to use strobes for some of my photographer, particularly macro, so I "knew" how to use flashes and then just made the decision not to use them.
Now, looking back, I realize I didn't know how to use them. Or rather, I knew how to use them, but to nowhere near their full potential. I can say with certainty that I wasn't sure how to properly balance artificial and natural light and that if I tried portraits with flashguns, they typically looked like those old high-contrast Polaroid shots.
In this video, Manny Ortiz goes through a technique he uses to make artificial lighting look more subtle and realistic, sometimes even giving the appearance of natural light. For anyone who isn't happy with how their images with flash look, work on balancing the light better to make it seem more believable that it's simply all natural.