God provided everything necessary for us to become a member of his family. He has done all the "legal paperwork." When Jesus died on the cross He signed the adoption decree, making it accessible "To whosoever believes in him." John 3:16 But he created us with the ability to choose to accept or reject the plan of salvation.
When we adopted our children, we signed the necessary papers and the the judge signed the final adoption decree making the children legally ours, even though they belonged to another family up until then. While the children are legally ours, they still have a choice to make, they can fully embrace Dean and I as their parents or they can reject us. We will love them regardless of their choice, just as Jesus loves us regardless whether or not we choose to give him our hearts.
Our hearts break when we are trying to help our children and they yell things like, "You don't love me, I wish I lived with my birth mom!" Sometimes I long for a way to prove to them just how much I do love them. I can give examples but in their pain, they can't hear or process my words.
Think how God must feel when we are hurting and come to him for help but reject the help he offers because it doesn't come in the form I was hoping or expecting. If we as human parents grieve when our children turn their backs on all we have done for them, how much more must Jesus grieve when we reject him and the plan of salvation he suffered to provide for us?