You can either itemize or claim the standard deduction. If you're itemized deductions are higher then it's better to itemize.

Mortgage interest is an itemized deduction and can be quite high, thousands of dollars of saved taxes a year, so there's incentive to owning a home and paying the mortgage.

Under he proposed plan it will be much harder to beat the standard deduction, so they'll be less incentive to have mortgage interest since you likely won't be itemizing your taxes.