Because the IRS just opened today to process tax returns. It may take a few days before all the e-filed returns that were pending get processed. You will receive a notice when your tax return is either accepted or rejected by the IRS.
Here is why. https://www.irs.gov/newsroom/2024-tax-filing-season-set-for-january-29-irs-continues-to-make-improvements-to-help-taxpayers