witness votes

Why would minnows just give away witness votes?
Witness run the block chain and are rewarded for their work. Top witness makes a lot of money. Some of them really work hard to get there but there are lot who dont even write a post.

Why wouldn't witness compete to get votes?
Mechanism shall include rewarding minnows for witness votes . Why would they take this for granted?
I think it will make it more reasonable.