Answer:
You cannot keep me until you have given me. What am I?
I am a protector of the scoreboard.
I wiggle and cannot see; sometimes underground and sometimes on a tree. I really don't want to be on a hook and I become a person when combined with “book”.
You seek me out when your hunger's ripe. I sit on four legs and smoke a pipe.
I am the minerals vital for your good health.
Whoever made me don't want me. Whoever bought me don't need me. Whoever use me don't know me.