you can download any music you want on youtube as mp3s. store them on a usb drive and plug it on your car, or store it in your computer and store a huge music library... but why bother yourself doing that if you can stream directly on any platform...
Because when you have your own copy of something nobody is keeping track of what the date and time is when you watch/listen to that media along with how often you do it or what parts you view/hear more often or pause at most often, or where you are and what other things you are doing when you saw/heard it etc. You can enjoy your media entirely offline which is something you'll really want if you find yourself without internet access for some reason. In addition, you don't have to worry about that content suddenly going away without notice, or it being censored or modified at some later date. You also get the ability to play that media in your software of choice and can even re-encode the media to play on other devices using other formats. You can make your own edits. You can share your collection with others without forcing them to create an account and hand money/data to a third party. You can include things in your own collection that those third party streaming services might not approve of.
When you give up on owning things you give up a lot more than just the item you would have had sitting on a shelf or the file that would have taken up space on your hard drive. There are lots of freedoms and opportunities you gain that wouldn't be possible otherwise.
Not everything can be streamed. Streaming platform are applying censorship. Not everyone is signing in to provide their music to streaming. Also they usually stream not original tracks, but a remaster.
