Why does God bother with us? We all reject God shattering any sort of relationship with him. Nevertheless, God acted in Christ reconciling us to himself.
We cannot provide a “why” for all this. We simply say God is love and he must always be true to who he is. He is love and he loves us freely. So, he would cease to be the God he is if he was not with us and for us bringing us back home.
In his triune activity, God does a new thing that takes us by surprise and yet he does everything according to who he always is. He is holy and righteous and yet, in his Son, he calls those who are his enemies his dearly loved children. He does not compromise himself in this. Rather he shows constancy to himself as love. He is true to himself as the one who loves in freedom.
The only “Why” is Triune Love.
Why do we now bother with God? Naturally we are not interested in him. Indeed, we are opposed to him. Well, Having sent his own Son as God for us the Father sends his Spirit as God in us. It is the Spirit who opens our hearts to all that God has done for us in Christ. And in the Spirit we respond to all that God has done in Christ with simplicity of heart. We open to his free turning to us as new every morning. This responsiveness to God is a gift, not an accomplishment. God gives us all that God asks of us. Our response is, therefore, a response to grace by grace.
The only “Why” is Triune Love.