Maybe people would have a better understanding of percentages if 20-sided dice were used more. "This has a 95% chance to succeed" -> roll a d20, anything but 1 is a success
Meanwhile 6-sided dice don't map to nice numbers, and having two dice makes the maths even harder to intuit
But (assuming two dice rolled at the same time) 2/36 is something like "roll a five and a six" or "roll either a pair of sixes or a pair of fives". Neither of which is quite as intuitive or commonly used in game design as "using one d20, roll a natural 20"
Meanwhile 6-sided dice don't map to nice numbers, and having two dice makes the maths even harder to intuit