I am a CPA and unless you have dealt with the IRS over the long-term, I think most of America has no idea how incompetent the IRS is.
You would be frightened if they prepared your taxes for any more than the simple return, ie some W2s. I would not even want the IRS to automatically prepare taxes for "simple" forms such as 1099-Int/1099-Div or 1099-B for stock sales.
And I do not say that from a "job security" perspective for the tax work we do.
The solution isn't government prepared taxes, it is less taxes.