There's a reason it's called a draft (preliminary stage of a written) sometimes you may want to recover your previous writing and with the draft that can be made possible. I once wrote a topic them preview it later I decided to edit my post before posting to make it more informative. I ended up deleting my last two paragraphs and when I preview again the sentences I added, sounded so dumb to me and I needed my old work back.  The draft because very useful and I got my previous work back so I don't support this suggestion of only keeping the latest preview.

For a draft to get filled up you need to be creating an average of 14.3 previews daily for a week so if that's the case then you need to slow down and get some rest.  No offends OP