Why should I do a whiteboard or take home assignment? Job I had in 2002 I did whiteboard and a take home assignment. I was hired but once I fixed the speed pro

Why should I do a whiteboard or take home assignment? Job I had in 2002 I did whiteboard and a take home assignment. I was hired but once I fixed the speed problem in their code running slow I was fired because they didn't need me because they got my take home assignment and white board info to give to the next programmer they want to screw over. I'd rather pop popcorn or bake pizzas than work with a company like that again.