Because they have specific temperatures and pressures at which they change state from liquid to a gas that we can use to keep food cold.
While there are other substances that change from liquid to gas they do it at temperatures that will not give us the cooling effects we need.
So, in other words, Cfc's have the physical properties that we need to cool things like food, to temperatures we like.
While there are other substances that change from liquid to gas they do it at temperatures that will not give us the cooling effects we need.
So, in other words, Cfc's have the physical properties that we need to cool things like food, to temperatures we like.