Edit: he also sells used video games.
PSA: Just because a dvd is shrinkwrapped, doesnt mean it is new.
CDs are in decline, but they're still a huge market (many, many millions). Consider just the millions of used cars out there which only take CDs and you can see why the market is still probably a huge business.
46% of music industry revenue still came from CDs in 2014. [0] That's at least hundreds of millions of dollars.
The next time you are driving through any random state and stop at a gas station or truck stop, you will see cassette tapes for sale. Those are from this guy.
You also have to consider he operates on massive margins. He gets his good for next to nothing and sells it for several dollars.
On drives greater than 30 mins, it's worth it, but if I'm just going someplace ten minutes away (i.e. most of my driving), well I'd be adding an extra 2-3 minutes just hunting down the cord, plugging it in, launching the player, choosing what I want to play, etc.
Meanwhile my CD player starts the instant I turn on the car.
That being said, I did get a Bluetooth FM transmitter recently that has a built-in SD card slot and starts transmitting the SD card music the instant you plug it into the cigarette lighter, so that may eliminate my need for CDs.