I’m not exactly one of the cool kids, but I use music CDs nowadays, actually, if only because they’re compatible with car stereo systems that don’t have support for newfangled gadgets (though I don’t actually own newfangled gadgets either)–our current vehicles at my house are a couple of Fords from 2005 and 2007. However, that’s for vehicles from the first decade of the 2000s. Coolthulhu’s not entirely wrong in observing that, at the very least, CDs are on their way out, even if they’re not completely obsolete yet IRL. In the world of Cataclysm it’d probably make more sense for the time period for stereo systems to require an upload of music from an MP3 player, E-Ink reader, SD card, USB drive, or yada yada, after which it ideally retains its “filled” status so you don’t have to keep the item in your inventory, but rather only need it if you want to use a new stereo system for some reason, like installing one in your house or another vehicle.
In the meantime, it’d be nice to be able to just leave the music CD in your stereo like you can in real life so that you don’t have to dig it out every time you want to use the stereo. Alternately, perhaps just an assumption that previous users already have their favourite songs uploaded to their stereo, such that each stereo system you find effectively includes its own music CD courtesy of whoever used to own the vehicle before they died and you came along to harvest the stereo/fix up and use the vehicle.
…Granted, this particular discussion could probably be had about things like the MP3 players and PDAs, too. The smartphone is gradually replacing everything else, such that by the mid-21st-century personal gizmos will likely just be smartphones and maybe E-Ink tablets if it’s important to retain a distinction of “this thing has more functions but eats batteries faster, while this thing has more limited functionality but doesn’t eat so many batteries.”
Requesting a Pip Boy atomic wrist computer that does all that shit.