I agree, however, I can create a Fusion Drive in my iMac. A Fusion Drive is basically software controlling the contents of two disparate hard drives. There have been people that have created a Fusion Drive out of an internal HD and en external SSD (not that it's very practical).
My poor DVD drive is basically dead - way too much r!pping. So I could replace it with an SSD and create a Fusion Drive. There are even kits for doing that.
Oh of course. But most people, let's face it, wouldn't have the slightest clue how to do that. :)