I use Obsidian but I don't follow the whole "second brain" thing, I just organize my notes by directories. You can use Obsidian however you want and adapt to the way your actual brain works. The "second brain" thing doesn't work for everyone. Even taking digital notes doesn't work for everyone (for example, it looks like you prefer paper notes).

If you haven't tried Obsidian at all I think you should give it a shot and write notes without following any system in particular. If you've tried it and you still prefer paper notes and the occasional apple note, then perhaps Obsidian isn't necessary for the way you take and organize notes.

> Could anyone enlighten me as to why to use Obsidian in one's daily life ?

My handwriting has degraded from consistent keyboard use over the last 30 years. Obisidan has replaced my paper notebooks, mostly because of this. However, it is handy to be able to mesh those notes with hyperlinks, LLM output snippets, quotes from other sources, embedded images, etc. Doing all of those other things would be laborious to impossible with paper.

Taking the notes (and being able to read them again if I want) is all I need from my "second Brain". This perfectly can be pieces of paper, as long as i can carry them around with me. More realistically some digital notes software fulfills that requirement.