It doesn't help that textbooks and course materials in mathematics sometimes appear to be designed for working mathematicians more than for students, with a lot of outright hostility towards the very concept of students learning maths.
(I acknowledge that this comes from Math professors hating the time they spend teaching STEM weed-out courses, but I still think that overall, Mathematics is much worse than even theoretical computer science at avoiding things like Notation Proliferation Syndrome and Greek Letter Syndrome that make it artificially hard to learn.
Explain the rigor, yes, but also explain the meaning and the concepts such that a decent learner should understand them well enough to reconstruct the rigorous parts on-the-fly as he or she needs.)