Now try giving that 2.5 year old a graphing calculator and see how well that works.
Now try giving that 2.5 year old a drum kit and see how well that works.
Now try giving that 2.5 year old canvas with a palette of oil paints and see how well that works.
The iPad is like giving you maracas, a tambourine, or bongo drums. Same functionality? No. Vastly more fun for beginners? Yes.
I think it has something to do with abstractions. There are no abstractions when playing a violin. You move the bow which causes strings to vibrate and that’s it. User Interfaces are built on abstractions. CLIs, mouse interfaces, touch interfaces, all are abstractions because nobody would want to edit a photo without those.
Just because the iPad uses different abstractions doesn’t mean it’s the computer version of my phony easy to use violin. I honestly think there are ways to improve our abstractions and the iPad might be a step in that direction. I also see no reason why a 2.5 year old shouldn’t be able to pick up at least some of those abstractions which are also fitting for grown-ups.
(I actually think that it’s possible to build better versions of that one example you mentioned that also uses abstractions: graphing calculators. Most graphing calculator level math is certainly too hard for 2.5 year olds, but when it comes to inputting stuff many graphing calculators suck. Incidentally, there is not a single great graphing calculator available for the iPhone. I really wanted one.)
Every one of those things you've listed have a _horrible_ user interface. My ability to make music, calculate complex equations, play the drums, and create art is seriously hampered by my inability to use those devices.
As a result, I am neither a musician, complex-equation-calculator, drummer, or painter.