Ethics of Owning Music

So I was recently working on my homework and I stumbled upon an interesting question regarding the ethics legality of owning and sharing of music either through CD or even digital downloads. What's your opinion?

CDs and DVDs Today

Today CDs and DVDs seem to be on the decline. All Macs no longer ship with a superdrive, Windows PC are starting to pick up on the trend to. So what happened? Although today how often do you find your self using a CD or DVD? Now they have all been replaced by online streaming services. There are endless possibilities to buy an find the content that you want to watch online so why get a physical copy?