why coins are made up of iron or other magnetic materials only ? Why are they not made up of steel or any other non magnetic materials?

In some countries coins are made of magnetic materials so that they can be picked up by magnets. In banks and markets there are certain machines known as currency sorting machines which count the coins. They work by picking up the coins using a magnet and then counting them. So to easily count the coins, coins are made of magnetic materials.
If they are made of non-magnetic materials they cannot be picked up using magnets and it will be difficult to count them using machines.