They definitely don't have all that information. That was my point.
And marriage and death records are public, as are probate. So they would have all of that too.
Or simply ask you if the most common situations apply to you, just like turbotax does.
The IRS could send a tax bill for what they do know, with an option to agree that is all you owe and pay, or an option that you will need to file the taxes yourself because they are missing information.
For the vast majority of Americans, option 1 will cover them.