Under ASX Business Rules they are required to provide quotes in certain option Series. This requirement is to ensure liquidity in the market, so that traders are more easily able to trade into and out of an option position.
Market makers compete against one another while trading on their own account and at their own risk.
They can be either individuals or firms. Each market maker is assigned two or more stocks in which they must meet certain obligations. Quote Requests - market makers who choose to make a market in response to Quote Requests must provide orders on request for all Series up to nine months maturity in a Class for the Minimum Quantity and at the Maximum Spread. The maximum elapsed time before responding to a Quote Request or replacing Continuous Orders is 30 seconds. The minimum duration of an order is 30 seconds.