If it doesn't have day-to-day application, does it really matter? I spent 20 years without using linear algebra. Now I'm doing a bunch of image processing algo

If it doesn't have day-to-day application, does it really matter? I spent 20 years without using linear algebra. Now I'm doing a bunch of image processing algorithms and it's suddenly relevant... and it's mostly coming back. And for the new stuff I'm learning I got a book which I occasionally read at work.