@goblin -- Other people have covered the idea of voter disenfranchisement pretty well, but I think there's something that may not have been explained that is true regardless of your political beliefs re: voter ID laws.
You don't (at least theoretically, given some of the voter roll purge issues that have been cropping up) have to register to vote every year or in every election. Theoretically speaking, once you register to vote, you should stay registered to vote provided that you do so every so often, don't move, and don't commit a felony in a state where that removes your right to vote, temporarily or permanently.
However, there have been issues of voter roll purges cropping up, so it's always worthwhile to check online -- which is really easy! -- as to whether or not you're registered and your registration information is correct. And there's people who only bother to vote in presidential elections. Or people who may be away from their polling place on election day that need an absentee ballot. Or who serve in the military, so they might be on base or overseas. Or are in college, so would need to change their registration if they wanted to vote where they go to school versus in their hometown. Or who have moved to a new area and simply forgot to update their registration. Or in my case I live in Pennsylvania, the most heavily gerrymandered state in the US. Recently (back in February), the state courts ruled against the drawings of district lines as they were and ordered them redrawn. My district -- which had been so heavily gerrymandered that my ZIP code literally had to be checked block by block based on your street address to figure out who your Congressional House representative is -- was completely redrawn, and the district I'm currently in versus the district my November vote will count for has totally changed. I used to be PA District 1 and I think I'm changing to PA District 3, or something. (I know the candidates, but keep forgetting the district ID.) For me, it was worth checking on my registration to make sure that my voter record had properly transferred and whether or not my polling place changed, so I don't show up at the wrong location and end up getting turned away.
So, yes, it's a pretty garbage system.... but until recently, for most people post-Voting Rights Act of 1965, the big problem was remembering to update their stuff by the deadline if their situation changed. Slightly less so with the overt "hahaha, you're poor/brown/foreign-born but a citizen/unlikely-to-vote-for-our-dickface-candidate?!? you don't get to vote!!!!" bullshit.
