The IRS has to implement and distribute the technical specs on new changes to the tax software companies and then once they are worked into the program and tested the IRS must also test them and approve them which takes time. Just because paper forms are ready doesn't mean programs are ready (which they are not ... they are still in draft status) ... not even my professional program is ready yet.
To do tax planning you can use the downloaded program by using the What If tool in the FORMS mode or make direct form entries in the FORMS mode or use the IRS estimation tool here : https://apps.irs.gov/app/tax-withholding-estimator/income-and-withholding
ANY tax software released by any company prior to about January 15 is only released for marketing and market share. No program is complete and ready to file until the IRS approves their final forms and then individually reviews each program's implementation of the form. And some tax situations aren't able to be filed until February or March, again mostly due to IRS delays.
