Frank Sinatra was probably close to the original "Boy Band(tm)". Singers were originally an appendage to the orchestra who was the big name. With TV, being young and attractive became much more important than the music and that equation flipped.

Sinatra, Elvis, The Beach Boys, The Beatles, etc. All of them relied on being "boy bands" to spread their music initially. Sure, many of them became more sophisticated with time, but much of their initial catalog was ... extremely derivative. There were a bunch of contemporary groups who sounded just like Elvis, The Beach Boys, The Beatles, etc.

Without being Boy Bands who could move records, they never would have lasted long enough to get better and become the legends we now know them to be.