I’ve used MIDI “as paint”.
Written music using code to MIDI(1), and wrote “cross instrument” music, ie using my keyboard as drum machine.
But these days MIDI is chiefly an archival method for me.
Every time I touch my keyboard is recorded, is much smaller than a comparable audio recording, by design “forced fidelity” in the recording, the music is “searchable”, and I am able to pipe the MIDI format through transcription software (which would be near impossible from an audio recording today).