Answer:
Many people own a copy of me. Without me the world would fall.
What gets sharper the more you use it?
I am not a toy though many use me for pleasure. I have a butt but I cannot poo.
I climb higher as I get hotter. I can never escape from my crystal cage.
Physicists have built devices to move me very fast. My last seven letters can be commonly found in newspapers magazines and journals.
Whoever made me don't want me. Whoever bought me don't need me. Whoever use me don't know me.