I think it's tough for elder celebrities to relate to the common man and I think as a result you don't get anything from them in their golden years that can really speak to you about on your level. An artist could've been the best lyricist musician, songs to make you empathize or even cry, but once they get a taste of fame, I think it's hard from them to have everyday crap happen to them anymore.
Sure, they still have their problems, probably more than most but they bring it on themselves and he's where they lose touch, they don't think they're the cause. They might blame someone else for their invented woes, so how can they feel the part of the victim to write the blues? Everyone else is just an idiot to them.
I just think elder artists, musicians in particular, can not write emotional songs anymore. They end up going country and sing about the exes that took everything. Bitter is the phase they enter. They write bitter or if they're still living the life of a rock star (Stones *cough*), sex, drugs and rock and roll! But no sad songs. Not good ones anyway.