Because it either has not yet been accepted or if accepted it takes 24 to 48 hours for the tax refund website to show the refund status.
Your tax returns will remain Pending until the IRS starts receiving tax returns. It may be several days after the IRS start date before your tax return gets accepted or rejected.
Go to this IRS website for the official start date - https://www.irs.gov/newsroom/irs-opens-2020-filing-season-for-individual-filers-on-jan-27
If accepted by the IRS use the federal tax refund website to check the refund status - https://www.irs.gov/refunds
See this IRS website for federal tax refund FAQ's - https://www.irs.gov/refunds/tax-season-refund-frequently-asked-questions
When you have transmitted your return to the IRS, you will receive two e-mails. You will receive physically separate e-mails for a state return, if a state return is filed, for a total of four e-mails. Two from federal, and two from the state.
The first e-mail informs you that you have successfully TRANSMITTED your return to the IRS. This e-mail usually arrives in 10-15 minutes. If you don't have that e-mail, then you did not finish the process.
The second email informs you if your transmitted return was accepted, or rejected by the IRS. If rejected, follow the link in the e-mail to deal with the rejection issue. This second e-mail can take as long as 48 hours before you receive it. Once your return is accepted, DO NOT lose that e-mail. It's the only solid proof you have, that the IRS accepted your e-filed return. Without it, should the IRS claim you did not file a return, you lose the argument. If it's not in writing, it did not occur.
Once you have that e-mail indicated the IRS has ACCEPTED your return, TurboTax has fulfilled the obligation you paid them for, and TurboTax is no longer in this equation anymore.
Just because the IRS has accepted your e-filed return, does not mean they agree with it. It can take 4 weeks or longer for them to process it. To follow the processing, you can do that at https://www.irs.gov/refunds It will take 48-72 hours after the IRS has accepted your e-filed return, before it will show up on that IRS website. (longer before they officially start accepting/processing returns 1/27/20)