1001
IRS successfully launches their own free Direct File - some of my fellow 'murcans are eligible
(sh.itjust.works)
For your simple[r] tax needs: https://directfile.irs.gov
Most of the listed states do not have state level income taxes. The only exceptions are Arizona and California. The rest of the states have no state level income tax. Alaska is the only state without a state level income tax that isn't included in this IRS scheme.
I imagine there is a reason all but two of the chosen states lack a state level income tax.
Massachusetts does. Per the IRS site, the tool won't help file it, but will lead you to another tool that does.
State taxes are probably an additional complication in the calculations that hasn’t been implemented yet for all states. And for those without a state income tax not covered, probably some other state-tax-adjacent thing