Depends on your definition of nu metal, I guess. Most nu metal bands are hit or miss for me. Korn, for instance has some good songs, but most I don't care for. The inverse is true for System of a Down. Even Limp Bizkit has a few songs I enjoy.
I guess the biggest reason I don't listen to nu metal more is that it simply doesn't interest me, musically or lyrically. I tend to prefer a variety of styles, which is why I enjoy folk metal so much (varies from country to country). As far as lyrics go, the amount of general complaining or angst just doesn't resonate with me. Not that I'm an angry person, but I'd rather listen to a band with kickass instrumentals and ignore the subject matter.