Yes, but penalties do so there is a big incentive to maximize income from penalties. I was hit by this recently, by not filing a no-income return, and not certified mailing another return that was lost, but I wasn't alerted until 2 years later when they levied $4k in late fees. It used to be easy to get out of these penalties, but there are several accounts from uppers at the IRS that they have been sitting in meetings discussing cracking down on fee collection, no longer waiving fees etc.

Don't oversimplify. Prosecutors also aren't pay percentages of the sentences they get, still many prosecutors are zealous to get longer sentences. Because it's their job. The job of IRS is to extract taxes, more they do, more successful they are. People like to be successful.

Though IIRC, part of "paying" for PPACA (really, just to get the CBO numbers to work out) involved increasing the IRS enforcement budget on the premise that with more money they could bring in enough additional tax revenue to produce a negative net cost.