Each time you click "Preview", a new draft is saved. That means you'll quickly reach 100, my oldest draft is often barely a day old (meaning 100 new ones were saved in a day).
As a result, I barely use the draft page indeed, unless I want to find back something that I accidentally didn't post yet.

I often keep a few long posts open on separate tabs in my browser, but save each of them into a text-file. I keep versions too, I just add the latest version to the bottom of the file instead of overwriting it.
I've lost some unfinished posts when closing my browser before I was finished. Most of the time, restarting my browser would restore unfinished posts in open tabs, but that doesn't work all the time.

I can answer that Some topics take a lot of time to create (including waiting for data processing). I like to start the topic while my ideas are still fresh.