You are correct that there aren't very many recent cases of proven in person voter impersonation fraud. But that really isn't the point.
The current systems in states without voter ID laws make it virtually impossible to detect such fraud. In other words, the absence of evidence here isn't evidence of absence. The issue is that such fraud is virtually undetectable and there are very strong incentives to commit such fraud.
As I've previously discussed, it is ridiculously easy in many states to commit such voter fraud. Individuals (whether Republican or Democrat) have strong incentives to commit such fraud if they are willing to commit such an act. Combine that with the fact that it is virtually impossible to detect when occuring or after the fact and you have a strong argument for such voter ID laws.
So, you decry the lack of evidence. Well, frankly, it is an unfair argument because the rules in most states rig the game against being able to find such evidence. It is sort of like demanding that a person visually prove that more than a few stars exist outside of our solar system while denying them access to telescopes and only allowing them to look during the day. Then, when they can only point to a few stars that are visible to the naked eye during the day, you then say it is proof that only a few stars exist. Ummm, no. You've rigged the game to where the individual can't find the evidence. This isn't a perfect analogy, but the point is sufficient.
That is why even many liberals (not to mention 74% of the populace,
Washington Post Poll Indicates Nearly 75% of Americans Support Voter ID Laws for Election Day | TheBlaze.com) support such voter ID laws.