Although the downloaded program becomes available every year sometime in November with the online following sometime in December they are NOT fully operational programs ... they are only beta versions which will required many many updates before it is complete. The final program and the state programs are never fully operational until late January at the earliest.
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.