Can be handy for jumping around in something that doesn’t have thumbnails generated yet. But I agree, it’s a bit of an anachronism at this point.

Skipping forward/back between scenes mostly. It’s either that or the time skip, which works, but is more work and less accurate.

A lot of times, I re-watch films. It helps with starting a film from a specific point, or skipping a boring scene.

Another reason is that I often show my friends and family some cool stuuf from between the films, like recently, I showed a cousin Neo vs Smiths scene from Matrix Reloaded, and I didn’t have to hunt for it.

Chapters make a lot of finding stuff easy.

Another use case can be, someone recorded a video of a family function and added scenes in post production for easy seeking.