Couple of notes.
1) The IRS itself gets most of the tax advice wrong that it gives out to taxpayers
2) Paying taxes is one of the few transactional relationships you have with your government. If you ask me, a government representative should come to your office and you should pay him in cash, not hide and automate taxes so that they disappear.
3) There is a difference between a simple tax system and a tax system that is simple to operate. Taxpayers deserve a simple tax system. Continuing to automate the byzantine monster we already have is a terrible, terrible idea. How would reform ever take place?
4) Think for a minute what this implies: that a government agency that is responsible for collecting money should also be the sole source for computing how much money is owed. Where else would you allow such a conflict of interest? Should the police come by your house to determine what crimes might have been committed? Would you want inspections by the local health department of your private cookout? Right now we have administrative courts and such, but the principle is fairly clear: reporting by the citizen, oversight and acceptance of reporting by the government, and the court system to sort out problems. You don't start putting everything in one bag under the name of ease-of-operation. That's whacked.
5) I do not believe these candidates campaigned on this. What I believe they said (or meant) was that the system should be simple enough to eliminate the burden on the taxpayer, not that compliance with a bad system should be automated.
As a side note, have any of these people ever created software or worked for a project inside the IRS? The guys I know that have could tell you horror stories. Testing alone should give anybody who knows programming and the IRS nightmares. This is a tremendously bad idea, both from an execution and a structural standpoint. When something doesn't work, the answer isn't to just do it harder or throw computers at it.
Having said all of that, having the IRS give you the information that's already been entered once so you don't ever have to re-enter things? Excellent idea.
ADD: Completing taxes is not hard because we don't have technology applied in the correct manner. It's hard because the tax code is a complex, unintelligible POS. The only people benefitting from continuing to hide the POS that the tax code is are those folks who made it complex in the first place (And will continue to add to its complexity the more that we ignore it)