Why do people always stop one step too short?

If there is no free will, the concepts of justice, blame, etc. still survive funtionally intact. If "chemical you" commits a crime, "you" are only not responsible if "you" is a metaphysical entity separate from (and that cannot control) the chemical you. But there's no evidence that "you" aren't simply the "chemical you", and therefore fully responsible for your crimes. If "you" are a metaphysical entity separate from the chemical you, then "you" do actually have free will.

This is only not true if the metaphysical you exists but cannot control the chemical you, which seems reasonable but like... you can move your arm right now, by willing it to be so. Either metaphysical you has free will, or your conscious experience is the chemical you. Either way, your conscious experience is either the same as or commands your physical form, and therefore is responsible for the actions that you take, and can be blamed and given justice.