However some states were able to implement their own systems separately...which is why sites like HR block don't offer free filing in Illinois. Illinois hosts it's own solution, on it's own website, very easy and totally free and no upsell.
I have such complicated taxes that I need to buy a "Premier" edition of TurboTax. It comes with "free" state, but what they mean is that the computations are free but they demand serious money to e-File.
Illinois website is so awesome that I simply use it despite the free state addin. TurboTax does the computations with almost no extra effort, so I use it for a sanity check, but there's never been a difference.