Video editors use software like DaVinci Resolve or Premiere Pro. When reviewing a cut, going full-screen interrupts the workflow (hiding timelines). Staying windowed leaves ugly OS borders. "Cinematic Viewerframe Mode" (as some call it) allows the editor to see the pure video output overlaid on the timeline without borders, making color grading decisions more accurate because the surrounding UI doesn't trick the eye's contrast perception.
Here, accuracy trumps aesthetics.
For users with dual or triple monitors, traditional full-screen is a nightmare. Clicking on a second monitor usually minimizes your full-screen game or video. Viewerframe mode solves this entirely. Because the content exists as a "frameless top-level window" rather than a "display takeover," you can interact with secondary monitors without interrupting playback. For traders watching live charts, editors scrubbing timelines, or developers debugging code while a tutorial plays, viewerframe mode better facilitates true multitasking.