For the record, this question is alluding to the same retro style units that have been documented several times in this guide. It is often wondered why designers seem to always go with aluminum to make their kettle. Well, let’s just say this; it is not a coincidence and there is a valid reason that aluminum is always the go-to.
There are two main reasons and the first is how well aluminum transfers heat. To result in a much better performance, aluminum is used as it will transfer the heat from itself to the food efficiently. Secondly, aluminum (in specific anodized aluminum) is also easy to clean due to its smooth and slippery surface.