Because the PSU in this particular pc does not have any molex plugs at all. And its number of SATA plugs is slightly limited, to two. Believe me, I wish I could do it with a molex-to-SATA splitter.

So this basically means a jumble of twisted up cables and adapters, it's quite ugly. I have some SATA splitter cables to do the power, long SATA cables jammed up in there, yuck. What I want to get ...

SATA splitter cable powers up to four Serial ATA HDD, SSD, optical drives, DVD burners, and PCI-E cards from a single connection to computer power supplies; Snug-fitting drive SATA power cable ...