You do, just plug a flash drive into your phone, or plug your phone into a computer, open file manager and manually copy your music, or use smart switch and select to nack up you music. You can set a reminder on a schedule to let you know its time to back up. I know you are asking for the process to be automated, but I don't think that's in the cards.
Everyone doesn't. Everyone can afford a flash drive, and probably has one. Just like on a computer, you manually back up stuff. If it's important to you, you back it up--by whatever means you have. As sutomated ad it is right now, the best you can do to automate the process is to create a reminder to do it. There are probably even apps in the Play store to do automatic backups and if you don't have a flash drive, OneDrive is free.
Music takes up a lot of space, and people have varying amount of music--just how much cloud space do you think they should allow you for free? They allow backup of your essential files. Music is not essential and, rightfully, should be backed up by the user.
