I'm with KW on this, and I am somewhat surprised by the ad hominems he got. He is simply pointing to a flaw he is seeing as a non-initiated.
And I thinks he's right: while not necessarily a flaw, I think it is a design decision that is not easy to defend. As an analogy, consider a car that had the gear shift on the top of the hood, and every time you want to change gears you'd have to reach outside -- but otherwise the car would be just perfect. When you complain about this design feature on a forum, the community lists a variety tricks: an extension shift, tag-team driving with designated steering and gear shifting roles, removing the wind shield, etc. Or the community lists a variety of advantages: it's a good stretching for one's back and shoulders, keeps you fit (kids these days do not get enough exercise), keeps you focused on the driving. Or the community criticizes you for not being flexible enough, wanting easiness and comfort in your driving. If you mainly want the car to take you and your friends from A to B, I think you are entitled to call the design unappealing -- despite the fact that the car is otherwise perfect and despite the community has accustomed to it.
For me, it is not that I cannot do the math or whip out a calculator, it's just that it does not add anything to the game. One gains very little from using the 1-100 range (I am not sure it is a percentile, as it is not a probability) while one loses the convenience of lower range mechanics. Some may believe it adds "accuracy" to the game, but if you have done you probability 101, the gain is a nominal one. The range 1-20 would yield pretty much the same functionality. A rule-system being fundamentally a more or less arbitrary (if consistent) collection of heuristics to represent actions in an imaginary world in the first place, scaling up the value range does not really make it any more realistic or necessarily better. If the chances of success are around 30%, it does not matter whether you roll d20, d100, d1000 or d10000. Some say the game is better if it can represent skills at 31%, 32% and 34% too, and it is fine, but I fail to see the advantage.
I used to remember 20-30 phone numbers, but with mobile phones around I just don't bother anymore. The most fluent guy with numbers I've seen was a plumber. At a construction site, he has to constantly add, subtract, multiply and divide measurements and costs.
// Edit: I don't know about Knoxville, but in Europe, engineering involves computers for a reason.