Let’s be honest: most writers will never face a copyright dispute. Most shared drafts will never be misused. Most critique partners & beta readers are trustworthy people who respect creative boundaries.
But “most” is not “all.” And the writers who do face disputes wish they had
documented their process earlier.
The cost of certifying a draft is trivial — a few minutes and a few dollars. The cost of not being able to prove your authorship timeline, in the rare case you need to, is incalculable.