When CD's came along in 1989, thanks to a collaborative effort by Phillips and Sony, a unique situation occurred. The CD's could hold a lot of songs, more than what a record producer would want to put on an album because they didn't want to give away the store so to speak. In other words, if they could make $10 by offering 10 songs, then why give consumers 20 songs for $10 especially since it costs money to record each song. The alternative was to charge more for an album which record companies didn't want to risk.
When all is said and done, most songs are still less than four minutes in length because the fact is, radio stations make or break artists and the record industry must offer them a product which meets their needs. Most CD's have around 10 to 12 songs even though a CD could hold seven times as many but whose going to pay $80 for a CD filled with 70 songs from the same artist?
Some products and services come and go, but throughout history, the music industry has remained highly popular. Last year it brought in over $50 billion in revenues.