I will admit that re-reading books has become less of a habit the older I get because it is time consuming to get through a longer series again.
For myself, the answer is "because the story is still enjoyable even if I know how it will end". And often enough, on a second reading/viewing I will discover nuances to the work I didn't the first time. Some works are so well made that even having enjoyed it 10+ times, I can discover something new about it! So yes, the pleasure of experiencing the story the first time can only be had once. But that is by no means the only pleasure to be had.
Most music doesn't have the same kind of narrative and strong plot that stories like novels and movies do, this is a massive difference. And even if it does, it doesn't usually take a half hour or more to do such a change. That's a pretty big difference about the types of art.