I'm not really sure either, but I think it's because of the curse words in Holiday from Real and the several drug references in MFEO, as throughout the album (or at least that's what I've read).
posted 4 months ago
huh, yeah, okay. I guess it's just much much less explicit than many albums with the warning...
Yeah, I didn't really find the album that explicit. When I first saw your question I couldn't come up with any reasons, and was like "Why is the album explicit?". So the reasons above is actually the results from a google search I did to find the answer :P