Why do you need salt on the ice when you can use ice cream maker to make ice cream?

Answer 1

"The salt makes the ice melt. the melting of ice requires input of heat and this 'sucks' the heat out of the ice cream mixture causing that to freeze."

You are correct. The salt lowers the freezing point of saltwater-ice mixture causing melting of the ice. Melting of ice is a process that absorbs heat due to the heat of fusion (80 cal/g of melting ice). Thermal energy is transferred from warmer (ice cream) to colder substance (ice/saltwater mixture). In this instance, heat is lost from the ice cream and transferred to the colder ice/salt-water mixture, allowing ice cream to freeze.

Answer 2

Ice cream is much easier to make in a compressor ice cream maker, which has a built in electric freezer. No ice or salt required. But this type of ice cream maker usually costs over $200, so if you only make ice cream rarely its best to use a cheap ice cream maker using an ice and salt freezing mixture to freeze the ice cream. The ice and salt are not part of the ice cream!