The real reason is that Americans owe money on more income than the gov't is aware of, and if you're going to omit income, they want you to explicitly lie about it so you can be prosecuted for it.
This is what I'd think as well. If they wanted to corner someone into explicitly lying in order to allow for prosecution, wouldn't they still be doing so by claiming non-standard deductions which they weren't actually eligible for?
> they want you to explicitly lie about it so you can be prosecuted for it.
Since “they” also define what you can be prosecuted for, that’s a bit of an odd justification even before considering the fairly strong evidence from both tax prep lobbying and anti-tax candidate behavior (including occasionally saying the quiet part out loud directly about the pain in the process being necessary to keep tax burden front of mind for taxpayers) that the two reasons cited by the grandparent are, in fact, the dominant factors.
Now is the punishment important part or eventually reclaiming it? In systems where taxes are done by agency and unreported income is found they still have to pay. Was pretty common with cryptos some time ago here.
“If you had any income that is not reported here, report it on irs.gov/…. Failure to do so is punishable by …”
This would make things significantly easier for 90% of the population.