Same issue as with tax fraud. Governments prefers dealing with mistakes and small frauds they are cheap fast success, simple to detect, no lawyer to fight back, but the opposite for large frauds.
This was explain to me by an accountant when I wondered why they wanted to have me fix what felt like I significant errors, mean while a big corporation was in the news for what was clearly tax fraud but the government was dragging they feet about it.
Corporate accounting is more complicated than family accounting. Even if the corporation isn't trying to do anything complicated!
Consequently, there are more edge cases and grey areas. As an accountant friend said to me, it's more like law than science -- knowing lots of laws and regulations, plus history, and deciding how to mostly correctly classify various things.
So something like trying to write the most efficient assembly algorithm possible, while Congress is modifying the ISA every year.
(Which isn't to say that loopholes don't exist, corporations don't abuse them, or corporate tax attorneys don't delay enforcement actions... but is to say that even in best case, family accounting is much simpler than corporate)
I don't think so in 2023. I worked several years in a tax agency and it was mainly a problem of "motivation". I have a friend who pursued "data warehouse" for 30 years there... nowadays you can crunch all the information and find patterns . I would even suggest that tax agencies should anonymize data and create data bounties to help them. In the same way DARPA creates cyberchallenges [1].
I think it'd be impossible to anonymize data in such a way that it's still useful but not easily identifiable with public or partial private information.
This was explain to me by an accountant when I wondered why they wanted to have me fix what felt like I significant errors, mean while a big corporation was in the news for what was clearly tax fraud but the government was dragging they feet about it.