We preferred quality over quantity
Blame the internet; the world wide web created an audience thirsty for free content. Listening to music was an investment, and if you wanted your money's worth, you were going to spend some time with it, too. As a result, for listeners, consistency was important; and as an artist, the ability to create a consistent project of the best possible material was important, too. Sometime in the late 2000s, though, the floodgates opened; by 2009, everyone was releasing free artist mixtapes, and they were no longer freestyles over industry instrumentals, but any and everything an artist recorded. The non-stop drip to blogs and livemixtapes.com meant quality control went out the window; the most important thing was generating as many headlines as possible, keeping an artist's name on websites so they'd buy the album when it dropped in Nevruary. And suddenly it was a race to the bottom, as every demo, half-hearted song and underwritten punchline made its way into one .zip file or another. Only the most talented rappers learned to adapt to the changing environment; many just killed quality control altogether.