You just pushed a major hot button. Where's the evidence of massive voting fraud? Please note: I don't mean voter registration fraud - the incentives that enable voter registration drives provide a significant incentive for voter registration fraud (cf: Acorn and the recent GOP sponsored voter fraud in the 2012 election).
However in a presidential election year, there are vanishingly small numbers of in-person voter fraud. In several elections where fraud was claimed (Washington's governors race in 2004, Minnesota's senatorial race in 2008), very few actual cases of fraud were uncovered.
In the US, there is almost no evidence of in-person voter fraud. If there were, I could see a need for voter ID laws. But there isn't. So what is the point of voter ID laws? Why would politicians be sponsoring legislation to address a non-existent problem?
One theory about why voter ID laws are proposed is that voter ID laws provide a barrier to people who don't have a government sponsored ID (since you need to have a government ID to vote and getting the ID can be difficult). It turns out that the set of people without government sponsored ID tend to live in urban areas (where the need for a drivers license is ameliorated by mass transit). And guess what: Urban voters tend to vote Democratic.