Because it is called demagogury.
Take a look at the video in reply #3, biden would make Elmer Gantry blush.
blogs.thestate.com/bradwarthensblog/2006/11/joe_biden_at_ro.html
"The clip begins right after he left the rostrum and waded into the crowd to answer a one-word question: "Immigration?" Note the passion, the waving arms, the populist posturing, the peripatetic delivery. Joe Biden has always loved to talk, but this Elmer Gantryesque performance went far beyond his routine style."