Well most obs users like the facility of composing scenes without having to check how to identify each window/input/source. I tend to favor cli tools but we are talking about video software and the ability to have immediate preview is really comfortable. Also I don't think ffmpeg can switch scenes comfortably. I am using obs to create some video tutorial at work. I could record different rushes but I find it more convenient to record a single rush with different scenes and cut the hesitations or repeated moments due to bad prononciation or cough or whatever afterwards with avidemux.

However this give me an idea about a tool that would export scene composition and video output settings to ffmpeg argument for easy reuse. It is true that if you don't have an usecase where you switch scenes it could be handy to start a record/stream from a command line. For example I have been ripping some videos from my streaming services so that my daughters can watch the movies on a plane, works great for that. Didn't bothered using ffmpeg because the preview allowed me to be sure I was recording the correct window without realizing 2h later I had recorded trash. Surely there are better ripping tool but at least this way probably do not attract attention from said streaming services as you are recording in real time.