Because you can never have too much flexibility.
Who could be bothered burning DVDs these days? If you've got important data to back up – like all your emails, youtube videos, work documents, digital photos and completely legitimate downloads – it's easier and cheaper to simply throw in another hard drive than waste your weekends cutting disc after disc of carefully categorised CDs, DVDs or even BRDs.
But to add that hard drive in, you're going to need power, and if you've already added a few hard drives over the years, you might be running short on SATA power cables. But of course, I have these handy little numbers that can convert any spare Molex power cable into not one, but two SATA power plugs. Now you can run two hard disks, optical drives or a combination of the two and all you'll need in addition is a spare data I/O on your motherboard for the new device.
Top quality Molex to SATA power conversion at a great price!