system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why are guitar, bass and drum kit the basic instrumental core of modern music?

Of all instruments (and of course a few of them are used very often - such as keyboards or sax, among others - though not as much as the "essential" ones in the title), why exactly is the vast majority of modern music genres based on those three instruments? Even the drum kit itself, why is it the way it is, with all the diversification of drums and percussion in the world? Is there a special reason for this quintessential instrumental selection? What made that happen, what explains its lasting establishment above all others and could they even become obsolete to music in the future?
gpt
They're the simplest method of providing a chord sequence, a harmonic backup, and a rhythm, all while being easy to learn, store, transport, and amplify.

The guitar and piano are the most common instruments capable of playing full chords - other lead instruments (think saxophone, trumpet, violin, etc) are only able to play a single note, requiring other band members to back them up to flesh out chords.  Of the two, guitar and piano, guitar is a bit easier to learn and to play simple chord structures, and it's much, much easier to travel with and set up.

The bass is popular for the exact same reasons as the guitar, except instead of a chord structure, it gives you a harmony, countermelody, and bass support.

The drumset is simply the most convenient way for one person to provide any percussion needed to keep a rhythm in various styles.  They're completely modular, meaning you can modify them with anything - tambourines, gongs, xylophones, whatever.