By completely ignoring music of the past you are ignoring the influences of the current music you like. You don't know where the artists you like are coming from or how much of their music is actually their creation. Listening to music with knowledge of the influences increases total comprehension of the music and makes listening a more enjoyable experience.
What really pisses me off is when the same jackasses who follow this sentiment say something like "I think that Artist X is the most original band of our generation." What?! How the fuck can you have any idea what is and isn't original when you have made a decision to ignore all music made in the past? When you make a decision to remain ignorant on a topic, you lose all rights to discuss that topic.
-Brandon