Yes, it's correct that there is a MIDI standard which relates to your question, but what you are talking about predates MIDI and has more to do with the history of sample-based keyboard instruments. The MIDI 1.0 Specification was published in 1985, but didn't include specific instrument voices like you are talking about, and was only an abstract communication protocol. The Instrument List was introduced with General Midi in 1991. (Wikipedia)
The MIDI General Instrument List likely just immortalized an arbitrary list of sounds available on existing popular keyboards. This article on the Casio SA-1, a keyboard from 1989, shows the list of 100 preset sounds available on that keyboard, which have considerable overlap with the MIDI Instrument List. The decision to choose 100 sounds works well with a two-digit selection interface which is still used to this day, and is pretty close to the MIDI list of 128 instruments that fit within a one-byte integer. We see a possible bias towards Japanese traditional instruments, such as shamisen, koto, and taiko drums, which would have been familiar to Casio as a Japanese company, as well as the mostly American and Japanese creators of the MIDI standards.
We can go back even further and see sounds that carried over from the original digital sampler keyboard, 1979's Fairlight CMI, which included a similar mix of orchestral and popular instruments, some sound effects such as glass breaking, and the "orchestra hit" sound that it originated.
There's certainly a lot more that could be written but I that's as far as I'll go researching this. It's an interesting historical question for sure.