Think of it as the difference between a computer algebra system and LaTeX. Sure, they're rudimentarily both about mathematics. But the former is about building

Think of it as the difference between a computer algebra system and LaTeX. Sure, they're rudimentarily both about mathematics. But the former is about building software that can do interesting computations with algebraic expressions. The latter is about building graphical representations expressly for humans. That's the difference between sheet music and MIDI. MIDI is extremely powerful, but it's not really about setting not just instructions but guidelines for human performers who will ultimately use their judgment on how to interpret it and perform it -- often in large groups. Compared to that, MIDI is not just way more low level, but simply for a difference purpose.