Because people are mostly some combination of honest and cowed by law enforcement.

I think it's harder these days than the other poster says, but there is still plenty of financial fraud.

There's usually more verification than just that. There's an automated system that asks about old addresses, employers, loan amounts/dates, etc. It's probably fairly easy to get that information but enough of a bump in the road to prevent massive fraud.

This is literally what "identity theft" is. It does happen in massive numbers.

Maybe it does happen all the time and you just don't hear about it. That's all I can guess.

My spouse's human resources dept was spearphished and sent all employees' tax forms. 1 in 3 employees called the IRS to get a PIN issued - the rest (hundreds) discovered someone had submitted fake tax returns on their behalf the next year. Many had credit cards issued to someone else before the credit lockdowns were in place. Any spouses or children whose SSNs were on the employees tax forms also had problems.