When you own music it's yours. You can do with it what you want. It's yours to enjoy forever.
With streaming all it takes is a dispute with a record label or an artist to change their mind and the music is gone. Like so much in the 21st century it's a matter of convenience. I love having access to millions of songs anytime I want them. However, losing that access to the music I love the most scares the hell out of me. For now I'll enjoy streaming with the complicit understanding that it's nothing more than a temporary rental, and make sure to buy anything that moves me in that way only music can.