Head units today use USB and/or SD card slots, so a hard drive really isn't necessary. A hard drive in a car isn't such a great idea since it is exposed to the elements (temperature extremes, humidity and worst of all, shock through road bumps), although a solid state drive would work well in that instance. I used to have this tiny USB hard drive for my JVC in-dash, and while it worked OK in most weather, it would not work at all in very cold weather since the disk could not rotate. Thumb drives and SD cards are much easier to load up in the house--I usually add new files once a month on average, with no proprietary software needed to do so. (Since my Pioneer handles FLAC files, I simply copy them over from the music server.)
Many new cars today do not have CD players. Someone in one of the automotive forums I read, found a USB-based CD player from China that worked perfectly. It was just a matter of finding somewhere to mount it. Manufacturers consider everyone just uses Bluetooth and their phones now for tunes (either stored on the phone, or via streaming), so they don't bother with CD players. Android Auto and Car Play both have a selection of music players and streaming services so even there, they see no need for CDs.
I haven't used CDs in cars for five or six years now. The USB thumb drives and SD cards hold up in all weather, don't get scratched up, don't skip or get dirty, are less to fumble with when driving, and (at least with the Pioneer I'm using now) I can carry lossless and better yet, high-res music files that surpass CD quality.
Many new cars today do not have CD players. Someone in one of the automotive forums I read, found a USB-based CD player from China that worked perfectly. It was just a matter of finding somewhere to mount it. Manufacturers consider everyone just uses Bluetooth and their phones now for tunes (either stored on the phone, or via streaming), so they don't bother with CD players. Android Auto and Car Play both have a selection of music players and streaming services so even there, they see no need for CDs.
I haven't used CDs in cars for five or six years now. The USB thumb drives and SD cards hold up in all weather, don't get scratched up, don't skip or get dirty, are less to fumble with when driving, and (at least with the Pioneer I'm using now) I can carry lossless and better yet, high-res music files that surpass CD quality.