Latest news about a pornography ring was caught, because the i.r.s. tracked the block chain. As a result they were able to find all the people involved. https://www.google.com/amp/s/www.forbes.com/sites/kellyphillipserb/2019/10/16/irs-followed-bitcoin-transactions-resulting-in-takedown-of-the-largest-child-exploitation-site-on-the-web/amp/
Duh. Why do you think all the services that support BTC need a valid ID and pic verified by a human to get started. Just saying, giant banks & retailers wouldn't support it at all if it was totally anonymous. Hardly anything is anymore.