If the ideal user is someone geared towards hearing new stuff, that’s an incentive to providing fresh sounds. It’s a good direction to steer.
About capacity-based systems, I could easily see paying a fee based on my portable/offline device, since keeping it stocked is an important bottleneck. On my PC I can easily find new sources, but offline I need and am willing to pay for more service.
Part of the deal there is that I use the device at times when I can’t fiddle with the music, like driving and working out. If the song file is corrupted I don’t have spare attention to find a new song.