11%-12% of the USA's economy is illegal activity. [2]
If you wanted to commit a crime or evade taxes, probably the dumbest thing you could do is record permanent evidence on a public, immutable ledger.
[1]: https://ciphertrace.com/2020-year-end-cryptocurrency-crime-a...
> Cash—anonymous and liquid—has long served as a tool for criminals. Cryptocurrency, with its similar characteristics, may likewise struggle to ever completely shake its bad reputation, despite illicit transactions making up less than 0.5% of Bitcoin’s yearly volume in 2020.
[2]: https://www.investopedia.com/articles/markets/032916/how-big...
> Estimates vary widely, but some put the underground economy at 11% to 12% of U.S. gross domestic product (GDP).