Because the program is still not fully functional and will not be for some time now.
These first releases of the program are usually very buggy ( you
are the beta testers even if you don't know it) and will require MANY updates
before it becomes fully functional which usually will not happen until late
January or sometime in February depending on the forms you need. So
patience will be needed as the IRS has not even announced when the 2019 filing
season will start
This past tax year, not only did the IRS have to rewrite a
ton of tax code due to the late changes made in Dec of 2017 but the fools
in Congress required they also toss out all the old form 1040 forms for
the new "1040 Simplified" version ( which is anything but simplified
since it adds 6 new schedules) and all these changes have the IRS way
behind the normal timeline so expect things to not only run late but they will
be VERY BUGGY so the smart money is on the patient person who waits to file
until most of the errors have been corrected. Last time this happened
many of the early filers had their returns lost or delayed for months so don't
be in a hurry to jump off that cliff.
