Because it was a law of sin and death.
(Rom 8:2 KJV) For the law of the Spirit of life in Christ Jesus hath made me free from the law of sin and death.
Paul tells how the new law in Christ Jesus has set him free from the law of sin and death.
Yet, for some reason, you still want the law of sin and death in your life.
So , he again asserts that Christ did not die to pay that penalty, of breaking His law, and taking the resulting
"sin and death" in our place, its' condemnation/judgment; His solution is to destroy, make void the law, so that there is no condemnation/judgment/sin debt, for which Christ might die.
Set free from its judgment/judgment, clown, meaning it still exists, by definition, BECAUSE HE TOOK THAT CONDEMNATION,JUDGMENT, in our place, i.e., substitution/identification, not because the law no longer exists, and thus it cannot condemn/judge anyone-that is from the pits of hell, and makes void Christ's death to pay our sin debt, Him taking the just condemnation/judgment in our stead.
Yet, for some reason, you still want the law of sin and death in your life.
No-Christ took that upon Himself. You deny that, and make a false dichotomy, that if the law is not destroyed, we are "under" it, it rules our life,and subject to it's automatic condemnation, so we must eliminate it, so that there is no condemnation. No,
we are dead to the law, meaning it still exists, as it is not dead to us, but there is no condemnation, for those that are in Christ, not because the law that condemns no longer exists;
Nea, it exists, but Christ took he judgment/condemnation in our place, paying the IOU, sin debt, for breaking His good, FOR EVER EXISTING, just law-JUSTICE SERVED.
That is the good news. Implicit in "good news" is that there is " bad news," that being we are all "guilty as charged" for breaking, by definition, an existing holy law of God.
You deny that. You lie. What is your motivation?