Maybe second brain is a misnomer. I rarely check old notes. Main value to me is lower friction to start writing and I spend more time reflecting. Keeping a daily log (ironically) improves my memory of what's happening lately.

For me it's also a place to dump all those things that you want to say but you don't know who to say it to. So you write it out and realize 90% isn't not worth saying to anyone. But occasionally a tidbit here and there helps in a conversation or meeting and it all seems worth it.