Sorting is such a foundational problem in computer science that pretty much every job will end up relying on the runtime of sorting algorithms. Not every job requires being able to write a bulletproof dual-partition QuickSort, of course, but knowing complexity bounds is important, even if you’re just calling your standard library’s implementation: it places fundamental bounds on what things you can improve.
Dev with decades of experience here - I've worked with a variety of languages and platforms, and across different domains. I'm not sure I've ever had to implement a sorting algorithm, or even had sorting as an optimisation issue (and I love micro-optimisation, a bit too much TBH!). I've had to sort things, of course, but standard (or at least "common") libraries invariably have sorting functions built-in.
Pretty much every job? I'd say about 10%. With all the web and web-adjacent jobs around, maybe even less. Most stdlibs are already written in a sensible way, so calling "sort" usually means calling quicksort. Most people just do not care, they have tickets and bosses to worry about.
