Why is it the contractual model of righteousness and reward – the ‘obey and live’ kind seems more acceptable to the human mind that the Christ your life model that is the new covenant. The short answer is that it panders to ego and sense of entitlement. You can think to buy yourself a sense of entitlement by a law-based contractual agreement. But keep in mind it is not recognised by God because He has gifted you with a ‘better covenant.’
‘He has made us competent as ministers of a new covenant--not of the letter but of the Spirit; for the letter kills, but the Spirit gives life’ 2 Cor 3.6 NIV.
The new covenant is not a ‘let it all hang out’ rationalisation of carnality. The new covenant is Christ in you – which we should take to mean – the reality of life itself in you and more: Reality in you. Life and reality in Christ are the same thing. Life is also righteousness but more than a balancing of good and evil like yin and yang. Life is the original perfect wholeness that was humanity in relationship to God before the fall. Today this life is yours and more as the union with God that is yours as a result of the cross. The trinity come to live in you, to impart to you their life and drive out all sorts of degradation and death from you. It’s personal, it’s communal and it is spirit and life.
It's not a contract. It’s a state of being.
As Watchman Nee might say, the contractual model of attempted godliness is carnal and attractive to the carnal Christian who has allowed herself to become enveloped in ‘ A Christian’ form of the knowledge of good and evil. The deceit of this tree is the notion the that ‘you can do it’ and that if you try harder you can do it on your own. Much Christianity is Try Harderism, which is not what Jesus gave us. Jesus’ gift to us is Himself woven into our being so that He is our life in every way and our righteousness.
‘Realize that I am in my Father, and you are in me, and I am in you’ John 14.20 NIV.
“As Simone Weil said in various ways, it is much easier to make non-Christians into Christians than it is to make Christians into Christians. Cradle Christians are almost totally preconditioned to the carrot-on-the-stick model.” (1) The real model, honoured so well in the breach is this: ‘God passed into man so that man might pass over to God.”’ (2)
When Christ is our life as Paul described and urged, we are not separate from God. God is in us woven into our being so that it is God who is entangled in our person. God who ignites our native sonship with His present Fatherhood and spirit and life. Then we are not so much ‘trying to be good,’ but one with Him we are living to be ourselves. Now we are the sons of God.
(1) Rohr, Richard. Immortal Diamond: The search for our true self. SPCK. Kindle Edition.