Are the Beatles the reason why modern music exists

Are You kidding ! Modern Music exists because of artists like Howling Wolf, Muddy Waters, & Bo Diddley. A big influence for the Stones is Slim Harpo. Jethero Tull, The Doors, Rolling Stones, Hendrix all played BLUES in the beginning. I love the Beatles but I am sick of hearing that penicillin was discovered because 'She Loves You' was herd playing in the backround. Early Fleetwood Mac,
Savoy Brown hasd a bigger influence than the Beatles. And What about Elivs, should he take a back seat to he Beatles.

If you had to pick one artist, I recommend that it be Les Paul, one of the pioneers using the electric guitar.

consumers between 15 and 25 are the reason it exsists

Sgt Pepper was indeed a milestone....a studio album that took you on a journey rather than just a collection of songs...IMHO, it kind of helped to create the rock opera era that followed where artists embellished and further explored the concept.

Louis Armstrong is the reason "modern music " exists. He and other early Louisiana jazz pioneers were the first to perform the solo instumental displaying extemporanious virtuosity. This is the basis for every guitar riff not strictly playing the melody and every "jam" session. Vocaly he invented "modern" pop (pun intended) singing. Every singer since (ella,Billy etc.)owes a debt to his phrasing and presentation. Prior to this it was choral singing or very,very bad pop singing. Later this jazz/blues style mixed with delta blues sounds like Sun House and Muddy Waters . This lead to people like Little Richard and the folks at Chess records which the Rolling Stones copied(stole) and the other modern pop groups which leaned heavily upon. So the Beatles used Louis's inventions with the deltas rythms and "whitened" them up a bit with pleasant harmonies for the mostly white pop audiences which created a sometimes very good "candied" version of some very seriously soulful roots. - Jim