[mst]

Winamp does have a library

Well, so does C1 now, but "back then" both didn't Sorry, haven't used WinAmp for more than a decade, I just used it as an example for your preferred style of workflow, which is folder-based. Been there, too, used folder and winamp exclusively, until I tried the iTunes way, eventually.

The advantages are maybe more obvious for music: easily find all music by Sting in your library, even if it's a single track on a compilation, or find all metal music from the 90s.

For images, JoJu summed it up very nicely. I use smart folders for example to sort the MTF shots by aperture. It's an empty smart album with subfolders by aperture setting. Just throw the whole set of test chart images at it and find it sorted as needed by aperture immediately.
Or search for images shot with a given lens... maybe not a common task, but a feature I use quite often when collecting sample images for reviews, especially for lenses I have used for longer than just a few days.