Which is just infuriating, because obviously (nearly) everyone has to file both.
It's like a restaurant telling you all their soda is free, but then it turns out they charge $3 for the paper cup it comes in, and you're required to use their paper cups.
You're not required to use their software to file the state return though. You can file the federal return and do the state return yourself. Many states like NC rarely have any steps beyond copying the federal AGI and multiplying by the state tax rate for common situations.
You're signing up to file your taxes for free and spend a couple hours inputting all the info, and then discover you'll have to pay or else now do your state taxes separately on paper and mail them in, taking another hour.
It's bait and switch. That's the problem.
This also reminds me of my apartment building, which has an “amenity fee” of $100/month for rooftop+gym usage, on top of the normal advertised rent. In the leasing office, I asked for details about it, and was told it’s a “non-optional” required fee which everybody has to pay. Stuff like that should be illegal - the only reason they would do that is to advertise lower rent.
States aren't charging citizens to e-file their taxes. At least I sure hope not.
(Personally, I also do my federal taxes manually, with the IRS's Free Fillable Forms. But either way, there's no need to pay for the state forms.)