Perhaps I'm just cynical, but I would assume to make it less pleasurable to vote against. It's not tough to imagine a blurb come election cycle along the lines

Perhaps I'm just cynical, but I would assume to make it less pleasurable to vote against. It's not tough to imagine a blurb come election cycle along the lines of "Senator X voted against anti-terrorism bills designed to keep us safe! Senator Y strongly cares about your safety, and the safety of the Nation. Vote Y. Vote America."