... the idea is that people who don't already have photo ID (for whatever reason, they don't drive or they're poor and have never bothered, etc.) aren't going to be arsed to go get it because it's required to vote. And therefore people who might have gone out and voted simply won't bother because they need to take an extra step first and now it feels like work.

You can make all sorts of arguments about whether or not it really matters, but what it comes down to is that such a rule will almost certainly reduce the number of people who vote, and the ones who are less likely to come out are the ones who are more likely to be poor or not drive. Maybe that's minorities, I don't know any statistics.

The idea that follows from that is that, on the average, there will be a higher percentage of votes from upper- and middle-class individuals, and the poor will not be adequately represented.

And yes, if the poor want to be adequately represented maybe they should go get some photo ID, but the fact remains that most of them won't, and the people making these requirements know that.

Why require photo ID? It potentially helps prevent or reduce any voter fraud that might take place. I don't know if there is any evidence that such fraud does take place, however. But most states do not require photo ID. However, some states do, so it seems that yes, it should probably be a state issue unless the federal government wants to make a blanket law that enforces one way or the other on every state.