They don’t have to. As long as Obsidian or any tool is working for someone then that is what they should use.

But for many including me Obsidian is not a solution for journaling although I extensively use Obsidian for note taking. You can read why here

• reddit.com/…/journiv_011beta_is_out_a_selfhosted_…
• journiv.com/blog/the-story-behind-journiv