Don't you hate it when you unplug a bunch of gadgets, but you can't figure out which power adapter is which?
If you're like most people, you have a bunch of power adapters connected to gadgets all around your house. My desk has at about 10 of them right now. The trouble is, they all look the same, so if I unplugged some of them, there's a good chance I would get them mixed up when I tried to put everything together.
Obviously this comes down to cost. Manufacturers are lazy and cheap, so they cut corners every chance they get, but they need to make sure every device they ship comes with a power adapter that's clearly labeled so you know which device they came with.