The IRS has to complete the 2017 forms and schedules and then the IRS has to approve the TurboTax forms and schedules that are included in the tax preparation software.
See this TurboTax support FAQ for IRS Forms availability - https://ttlc.intuit.com/questions/1908854-irs-forms-availability-table-for-turbotax-individual-perso...
Additionally, the IRS will not be accepting any type of 2017 tax return until January 29, 2018 so there is no rush to file a tax return.
