I just read Dave's reply post  to Edna's balloon question and the reason may be something like that.
There's more to music than just music.  It evokes freedom and spontaneity .  Sometimes you need a little music and there's no good stuff available.
STORY:
Many years ago I attended a county fair.  It was a little county and the fair didn't summon any big names but it was a Fair and I was new to the area and hungry for company--even from people I didn't know yet.
Late in the evening the fun was wrapping up and the band played their last number. "Desperado".  Suffice it to say they were not the Eagles or Linda Ronstadt. But:
The shadows were long and a breeze was picking up and it blew the papers and pieces of comestibles-past across the unpeopled grass.
And the wavering voice called people back to an everyday world.
Terrible music but wonderful in its way.
I had to smile.

Anita:  To twist an aphorism, your question begs the answer:  It's because those people don't know good music from bad.

"Why don't people demand/recognize/reward quality in everyday objects, in everyday life?"
I agree that this is a deep lament, which takes many forms. Think not just of the musicians, but the chefs walking past bakery after bakery filled with mediocre bread, past children on the subway stuffing themselves full of Doritos, or grumbling to themselves on yet another airplane flight listening to the food tourists en route to Europe make quick work of the plane food without much complaint.
Think too of what the dentists and the physical therapists and the fashion designers must feel.