That's true, but all of them have/had a lot more "mathematical maturity" than most programming 101 students today (who are often middle/high school students, un

That's true, but all of them have/had a lot more "mathematical maturity" than most programming 101 students today (who are often middle/high school students, university students who didn't do particularly well in high school mathematics, or even independent learners coming to programming from non-STEM backgrounds). SICP is not an introduction to programming as much as it is an introduction to computer science. I mean, one of the key lectures is about differential calculus. Do you realize that at most universities, CS 101 students are not assumed to have taken calculus. Hell, a large fraction of CS 101 students will NEVER take calculus (non-majors who will instead opt for college algebra). But that example itself is actually more of a red herring. The point is that the mathematical maturity does provide a lot of extremely useful background thinking/problem-solving skills that most CS 101 students haven't yet developed and will be developing for the first time in CS 101.