God cares. God cares because He craves fellowship with His creation. God cares because He desires to bless me and provide my needs and to pour out His Spirit upon me and then use me to reveal His great love to others. God cares because God is love.
Recently, a couple who is very dear to me began fostering a young child who, by all indications, was most likely abused. The child seems a bit distrustful of men. The foster dad desires a relationship with the child and is excited when the child responds to his kindness. Slowly, he is building a relationship with the child and every positive response from the child absolutely lifts his heart. I believe this is how it is with God. Our desire for Him lifts His heart! We are hurt by people because people are broken and we distrust God because He becomes one more person who has the opportunity to let us down or take advantage of us.
God is not human and not bound to human weakness and sin. God is not selfish or self serving that He should harm us, not even inadvertently, for His own agenda. Everything in all of creation screams of God's love for us. The LORD your God is in your midst, a mighty one who will save; he will rejoice over you with gladness; ; he will exult over you with loud singing.
Why should God care what I do? Because He wants what is best for me, He wants to reveal His great love to me and He wants to reveal His great love through me. That's why God cares about what I do!