I'm mildly surprised you didn't know calculus before becoming a software engineer. I suddenly realized that I falsely assumed calculus would be common knowledge to all programmers and now I'm wondering what else would not be that I've been assuming.
I taught myself programming after graduating from art school. I never took calculus or trigonometry even in high school, so my math skills are as basic as you can get as an adult.
Still, I'm currently trying to teach myself math because it seems like it will help me improve as a developer. It's very hard, though, to learn this stuff when you're 32.
It could be age related cognitive decline, real or imagined, but it could also be prioritizing any of the following over learning largely irrelevant mathematics: children and family, exercise, bills/finances/health care, social obligations, politics.
Plus, it's much more likely for a 22 year old to be able to go to college / grad school and be required to learn math.
I can assume 8/10 web developers aren't proficient in calculus, especially the ones who switched careers from non-STEM fields or those who graduated from coding bootcamps.