As others noted, this has background recording functionality and manual on demand recording as well. I have used manual recording software and still have OBS installed for any use case. But having Steam Recording builtin is very convenient.

1. configuration, its much easier to setup than any other solution if you care to get best quality and performance
2. convenience, integrated makes it easy to setup and use, with additional features, plus its such a fiddling to record specific windows when using external software such as OBS or similar if I don't want to record entire screen in windowed or fullscreen mode, especially on Wayland
3. performance, Steam records the raw game footage from your video card and therefore has the best possible quality and performance one can get out of video recording
4. no overlays, Steam will only capture the game footage without fps indicator or other stats and without overlays or menus from Steam, other software would just record everything visible
5. timeline, resulting video is raw footage and is not encoded into a video file format for output and not useable before output to video (mp4), we can add timestamps with hotkeys while playing to mark specific points in recording, then we can mark start and end points or select certain parts in the timeline to save or export it
6. share, it has multiple sharing functionality besides saving to mp4 video file format

All of this is builtin and works the exact same way regardless of operating system and hardware (independent from cpu and gpu and os). No one needs to study hardware and software in order to configure it in the best possible way. If you used this on Windows, its the same on Linux, no dependency of recording software.

This is a much bigger deal than just recording footage with gnome-screenshot.