Voter registration deadlines are a tool for paternalistic racists and classists to enforce their voter suppression agenda with the thinnest veil of plausible deniability. Here you are, declaring their denial as strictly plausible.
Maybe we could have voter registration deadlines if there weren't so many bad actors who use it as a tool for voter suppression, but apparently ~50% of US state governments can't be trusted with that responsibility.
Edit: that's actually the issue, inherently; many rules and requirements for voting sound reasonable when presented absent of the context of the entire history of the United States (especially in the apartheid South...), but there are literal neo-Klansmen who will twist and bend those rules into onerous requirements that make sure that only white wealthy people who live in certain zip codes and have plenty of flexibility in their schedule have an opportunity to vote.
And you fall for that trap with some sort of rationalist aloofness that's so common on this Silicon Valley technology forum. This is why being "woke" matters and the Trumpist campaign against historical literacy is critical to keeping certain states red. The historical literacy in some of these states is already abysmal (based on first-hand conversations), and to think it could get even worse...