Many itemizing taxpayers do not itemize on the New York return. You have to exceed the standard with property taxes, charity, interest, medical over 10%(or 7.5%), etc. On top of this, the itemized deductions adjustment on line 13 of the worksheet impacts many taxpayers. This removes some of the itemization benefit
For instance, if your NY Adjusted Gross Income is $150,000 and your filing status is single, your adjustment would remove 25% of your total NY itemized deductions from being usable.
This is the worksheet:
https://www.tax.ny.gov/pdf/current_forms/it/it201d.pdf
You can see the adjustment worksheet on page 39 of the instructions:
https://www.tax.ny.gov/pdf/current_forms/it/it201i.pdf
