COA's are not only helping in assuring authenticity, but they also often record other important information, which in my opinion is a good idea. Not saying they are the only way to record provenance, but they can be a good way, and many pieces are worth it.
30 years from now, or after the piece goes through a few new owners, the story that goes with your point today could easily change. The COA which could accompany it would hold the original/accurate information, and would likely be appreciated by future owners.