On a related note, the IRS also requires that you report and pay taxes on all the money you made by robbing banks, selling drugs, and embezzling your employer's coffers.

Nobody who hasn't already been convicted will fill out those forms, of course, but that's another criminal charge if the DA wants to put you away for even longer.

The IRS and the DA are different people.

The purpose of the IRS is to collect tax on income, not to punish people for obtaining that income illegally.

Sure. But if the IRS comes across evidence of tax evasion, they'll be happy to pass it along to the DA.