years ago i used to hang around with musos way way more technical than i or my fellow rock buds.
they were heavy into advanced jazz and chamber music/chord theory/structures. nice blokes too.
but they were always complaining to us "you stoopid rockers with your stoopid 3 chord songs...
how come you get gigs with those easy chords C5 or D5
or whatever." many comments in that vein.
but we said "we just give the people what they want.
often they have boring jobs and just want to party at the weekend".
Back in the 70's a band could learn 50 "pop songs" that everybody knew from the radio, and play anywhere, and you could feel relatively certain you were giving the audience what it wants. Not so true anymore. There is a worldwide glut of music, both pro and hobbyist. Spotify and Pandora have exposed people to so much music that there is no common denominator that appeals to "most audiences". A band would have to know thousands of songs in multiple genres to even stand a chance of playing enough gigs to make money.
In my opinion, that's one reason why DJs took over the wedding gigs. Not many bands know enough songs to entertain 4 generations... but a DJ can show up prepared with exactly whatever song list the bride requests.
And on top of the huge diversity of musical taste, there is also music snobbery. Who wants to invest years of practice and untold thousands on gear, only to receive disdain from every audience because your music isn't THEIR music?
AT least online streaming lets a musician use his/her gear without having to move it, and the audience is free to click away if they don't like it... so the people who stay tend to be appreciative.