Pads can define multiple layers in one go (For most SMT pads it makes a lot of sense to have copper, mask and paste defined by a single entity. Similarly with THT pads. Here you want all copper layers and top and bottom mask defined by a single thing.)
In reallity only the layers listed above are needed for the device to function. Every other layer is to make it easy on the user. (Add documentation, Ensure clearance between parts is correct, …)