A lot of that is caused by American income being separated into different streams. Your base income, your health-care insurance payments, your FSA or HSA contributions, your 401k matching, your stock grants (ha!), interest on savings accounts, etc, etc, etc.

Some of these secondary income sources send you tax forms in the mail, randomly, that look like junk mail.

So whereas a normal person earning 90k in the UK just gets paid, a person earning 90k in the US has to do the same level of paperwork you'd expect from a rich and enthusiastic investor with a thriving portfolio.

At the end of the form it says that you affirm that you believe everything is correct, under penalty of perjury, which can really knock you for a loop.

So the tax-prep firms charge you to do all this paperwork and offer you upsold insurance that covers you against accidental perjury.

It's wonderful.