Yes, all of those low-level tax evaders with their thousands of dollars in Bitcoin avoiding taxes via easily traceable transaction and plenty of digital forensic evidence! That's the real concern preventing bitcoin's adoption by legitimate businesses. /s
The IRS could employee <10 people fulltime to monitor these guys each year and not break even in returnable taxable income...
There are far bigger problems with cryptocurrency adoption/scaling that are tirelessly being worked on.
Money laundering and tax evasion via cryptocurrencies has hardly resulted in any level of significant criminality, despite the endless years of FUD/hype that it's attracted...