Helmut Newton was another Rolleiflex TLR user and had quite a few of them, he did use other cameras though. Nicolas Tikhomiroff another nearly Magnum Guy who liked his Rolleiflex. Herbert List Magnum and Rolleiflex. Raymond Cauchetier the photographer of the Nouvelle Vague loved his Rolleiflex and even left Magnum because of it. All four created their most famous work with Rolleiflex TLRs. Many LF guys only use one lens for most of their work.
There are many more photographers of mention who used only one lens than there are who didn't. One thing to notice when looking at this is that most stay in the slightly wide-normal to slightly long-normal range, avoiding extreme wides and telephotos.
Using one lens is an easy way to start getting some optical consistency in your photographs. It helps link images in the same way subject matter does.
Look at Keith Carter's first 4 or 5 books: Hassy with an 80mm. Doesn't get any more classic than that. Keith doesn't lack for passion or imagination, either.
I saw a "photographer" in Piedmont Park once, and he had three bodies with different lenses hanging around his neck, plus a fanny pack and two shoulder bags. It was hysterical. I wish I had made a photograph of him because he kind of had to waddle with all that gear. You just can't work that way...
With one lens, you think about the subject, and where to place your feet and your body in relation to it. With more than one lens, you start thinking about lenses!
How can anyone use more than one lens at a time? Shoot two cameras simultaneously? :-)
A TLR comes to mind
“Photography is a complex and fluid medium, and its many factors are not applied in simple sequence. Rather, the process may be likened to the art of the juggler in keeping many balls in the air at one time!”
Ansel Adams, from the introduction to The Negative - The New Ansel Adams Photography Series / Book 2