Creating a verifiable trading track record is shockingly difficult.
To do it, you have to convince the person on the receiving end that
a) What you're showing is complete and tamperproof. If they suspect you can go back in time to change any element of your record or that you can present an incomplete record (e.g. missing trades, accounts, start times, etc), your track record loses all credibility.
b) You haven't cherry-picked the best of your many outcomes. How do you show that you haven't run other strategies the recipient isn't seeing?
Plus, you have to do this while making the data easy to parse and analyze. Few people will spend hours parsing statements, trade data, etc.