Midi keyboards is still relevant today in the music industry. a colleague of mine uses his Macbook to play the piano, the "piano" is just a USB MIDI keyboard, so his options is open, playing from SFX to flutes on the thing.
So, everytime you see a MacBook on top of someone's "piano" or keyboard, it may be the music making device, and not the keyboard itself.
PreviousIy, thought they used Macbooks as the digital sheetpaper display. They could have used iPads for that.
Have you heard of the T2 Chip on macbooks causing amok with the USB2.0 devices (MIDI to USB, USB sound cards which is not USB3.0) which caused audio pops/clicks and more?