I think the main reason Matinees are used for the beginner tutorials is that it’s easier to grasp, letting you manually move meshes and playback the animation to see exactly how it’ll all look. They’re really more for cinematics, or environmental sequences like, say, a collapsing bridge, or some other event that would require moving a lot of actors around together.
Timelines unfortunately don’t give you any sort of preview and need more manual setup, but the upside is that you can use their outputs for a much wider range of things besides just moving objects around. It’s ideal for things like doors and levers, where you just want something to move in local space. If you set up a door Blueprint with a built-in trigger and a Timeline for opening, for example, you can re-use it all over the place without ever having to do any extra set-up, which isn’t possible when using Matinee.