The reason that life had to come by the promise, was that it had to be by choice, by faith. It was the response to the promise that God was looking for. Spirit cannot come by law, it comes by promise. And the Spirit makes the person, the person cannot be made by law conformity.
For this same reason also, those who reject the notion of this, are rejecting the notion of grace, so they can remain within a system of law. That means they are looking for a system where life is “earned” by conformation to a set of rules, precepts, laws or doctrines.
They reject the “buddy system” of Christ in you, the hope of righteousness. Their hope is instead, placed in the written word, the “Torah”, and they seem to believe that the reason Christ has liberated them is so they can keep the law.
Why don’t they simply become Judaists?
The misuse of the particular verse that refers to the law being kept involves Rom 8-4, which shows that the requirements of the law are met by those who walk in the Spirit, not by those who walk according to the flesh. It is those who walk by law who are walking in the flesh. Sin/flesh/law/death. Instead of righteousness/Spirit/grace/life.
Those who walk by the Spirit are walking by the very nature of God, not a limited written sample of his nature on a list of do’s and don’ts, which in any case are now redundant. “Now that Christ has come, we are not under the law”.