Have you ever held a magnet up to them? They might just be aluminum coated to prevent what’s shown in the image.
There are a few manufacturers that make magnetic case fan filters and such, that wouldn’t make sense if most cases were full aluminum.
Maybe you still had aluminum cases, but then they were probably also rather expensive, because it’s more difficult to manufacture in that thickness without being brittle.
Last couple cases I had and still have are aluminum
Have you ever held a magnet up to them? They might just be aluminum coated to prevent what’s shown in the image.
There are a few manufacturers that make magnetic case fan filters and such, that wouldn’t make sense if most cases were full aluminum.
Maybe you still had aluminum cases, but then they were probably also rather expensive, because it’s more difficult to manufacture in that thickness without being brittle.