[missedthecue]

But most Americans have at least a few deductions. How many Americans have offshore income? Especially the ones that would be relying on gov. tax prep?

In this case, it is mostly one sided

[runako]

See: https://news.ycombinator.com/item?id=32513370

Roughly 90% of Americans file using the standard deduction ($13k for a single person, $26k for a married couple filing jointly). Median household income is ~$67k, so the median household is not itemizing.

The remaining 10% of people would not be bound to use the free public system.

[missedthecue]

You can qualify for a number of deductions without itemizing.

[runako]

Correct, but in that case there is no impact to your taxes.