Bookmarks are useful for address bar autocomplete back to a site I know I visit semi-regularly, but for whatever reason disappeared out of my browser's autocomplete history. E.g. this might happen for social media sites that I only ever visit inside an incognito tab to try (probably in vain) to mitigate being tracked across visits. But also it can happen when I try a new browser or my phone resets itself or whatever. Then I just export the bookmarks.html from my laptop and import it on whatever other device.

I never bothered to look at the schema of the bookmarks.html, because feels like it's worked the same for 20+ years. I used to care a lot about housekeeping the structure, but it doesn't really matter, as long as they're in the bucket the browser will use them for autocomplete suggestions, so...