I like to be able to read the materials and have my notes with me when I'm voting. I can search online if there are updates or explanations that are more recent.
I also can't guarantee how long the lines will be on election day. I spent four hours in line to vote in 2016...and ordered pepperoni pizzas. It's easy to peel off pepperonis. I have obligations and some are time-based, like feeding the dogs. Three hours late, not happy dogs. Three hours waiting to be let out would be unhappy dogs or mess to clean up in the house.
My life isn't always my own, so voting early makes sense for me.