Let me explain.
I have been playing the piano professionall y for 65 years. My repertoire comprises several thousand tunes, ranging from the 1890's to 1980. It includes most of the "standards."
There is considerable irony here. Sixty-five years ago I was eighteen years old. At that time, seniors loved to hear me play. Here's why:
mother and father both had extraordinarily fine musical ears. My mom not only knew scads of songs;
I was the first of the children and at age 9 began piano lessons. As my piano-playing skills evolved, I started playing "by ear" and by the time I was 18, I had a considerable repertoire of melodies in my noggin. I naturally learned a style of playing which stuck faithfully to the melody. (This was to have a curious result when I attended school at the Potsdam, N.Y. Crane School of Music which was in 1947 swarming with young "jazzers." But that's another story.)
Of course, while I was in college, I regularly played the piano on "jobs" (now called "gigs") in the area. After graduation, my career began in earnest as a school music teacher and professional player. During these years, I and my cohorts were regularly picking up on the latest good tunes and adding them to our repertoires. Then, in 1955 something happened in the music world, which made most musicians feel uneasy. It was the advent of Elvis, and the cataclysmic effect he had on popular music! Rock-and-roll was born and music would never be the same.* And it was not only the music that was changing; it was its general characteristics. The electronic age had arrived and with it, massive amplification and a new element: distortion. Most of this new music could no longer characterized by gentle terms such as "mellifluous."
Younger folks took to it with a vengeance!
The so-called "golden age" of standards had ranged from about 1920 to 1945. You must remember that the principal sources of popular songs during those years had been radio, movies and Broadway musicals.