>I never understood the purpose of doing the daily note for these apps

I mostly use Obsidian for taking notes during D&D (arguably its killer app), but I think "session" notes are a good enough analogue to "daily notes".

To that end, these notes serve as an excuse to force you to list your individual notes in chronological order (which makes it easy to trigger further memories/details that came next), which then prompts you to spin out any specific-enough information into atomic notes, adding backlinks which provide context and organic categorization that might not otherwise be obvious.