Miners' main function is to secure the blockchain, not to create new coins. The term is a bit of a misnomer. Without miners no transactions could be made, so Bitcoin would become worthless. More rudimentarly miners simply inject expense into the chain, making it too costly to hack. Another (imperfect) way of thinking about it, is that miners pre-hack the chain by doing all the brute force that a hacker otherwise would, making it unhackable.