I try to (re-)learn math periodically because I feel like I should, like how one ought to eat one's vegetables and one ought to exercise, but extrinsic motivation is the thing that's lacking. I usually end up on recreational math puzzles or something, before dropping it, since at least those are fun. Probably made three or four cracks at it in a decade, each has gone the same way.
I literally don't know what I'd use most of it for—I can't find that need, even when I try. I'm sure I could make something up just to have an excuse to apply what I was learning, but... why? Probably there are other jobs I could find where knowledge of math was absolutely key, but... why? I've been paid to write code for about 23 years, my pay's great, and I've repeatedly gained a reputation at companies for being the guy to go to for tough or low-level problems. But if you gave me an intro to linear algebra final or calculus 1 final, today, I'd be lucky to score 25% on either (hell, I'd be lucky to get anything right on the Calc final, but maybe there'd be a couple easy questions at the beginning—I've never, once, ever applied anything I learned in calc, for any purpose, so what little I knew about it to begin with is long gone)