Almost everyone declines, the problem is how much. A Professor sounding* slightly* less sharp at 62 than he is at 42 - even if he's kept up to date and regarded highly in his circle still - would have been totally acceptable.

Biden's totally falling apart like a (I'd think) typically senile person is just sad. You wouldn't disgrace a normal senile person by shoving a mic and airing his incoherent and/or just down right stupid answers on live National TV to 5 million people, right?