I think a big part is that a piano is laid out in a perfect row of keys. It maps one-to-one with the musical staff in a way that’s very easy to see. This is different from say a guitar or violin where you can play the same note in different places on the neck on different strings, or from a horn where the pattern of keys that you press doesn’t always relate in an obvious way to the pitch of the note. A piano has a very literal and non-idiosyncratic “user interface”, which makes it easier for learning musical concepts on, especially early on.
Yes, good illustration.
Now to find the time to get started.......again...