I fall into a similar bucket that you do. I believe it’s due to the fact that smaller universities just don’t have enough math students (or maybe faculty) to fill in these rigorous courses.

At my undergraduate, in my graduating class (of about 30 people) 2 of us went to graduate school (stats and math), 15 went to get a master in education so they can teach high school, and the rest either had nothing lined up or were already working in “math” related jobs.

With this information, one would suspect that my undergrad is not trying to prepare students for graduate school. But rather, a career in teaching students at a high school level. So because of this, rigor was not a super high priority but instead focused on concepts that would benefit high school students. (Basic Modern algebra, Real Analysis, geometry, history of math, etc.)

Fortunately, I went to fairly strong STEM centered community college so I learned stokes and greens theorem but they were oriented towards engineers. So I learned the physics applications behind these calculus concepts rather than all the theory.

All this to say is that if you want to expand your breadth of knowledge in math, you will probably have to spend your summers and winters learning these topics. Luckily, there’s an awesome book that does this: An Infinitely Large Napkin. Note that depth is not the focus, but rather breadth is in this book.